BMW and Mercedes have that market sewn up.
They’re small, only seat 2, and are difficult to get into/out of. High performance roadsters are just not practical for most people, and those who want them usually have a few bucks to spend.
I would love to have a little sporty-looking car. I don’t have kids, I totally don’t need the back seat, I rarely drive far in my car, and I hate the boring little cars that are out there. I kind of want a two door hatchback just to be different!
There is definitely a dearth of affordable but sporty cars out there these days, but if you look hard enough, there are a couple. Until I settled on buying a new Mustang earlier this year, I looked long and hard at the Hyundai Genesis Coupe, which has styling I find hearkens to Aston Martin, while still remaining affordable. Toyota has a couple concept cars that they may release in a final form in the not-too-distant future, including the FT-86, which I think is slated to be on the showroom floor by 2013, and the FT-HS which may or may not ever come to fruition as a product. Of course they used to have the Celica in their stable, which was a slick little unit for a long, long time. Obviously, we’re not dealing with Ferraris or Lambos here, but affordable, exotic looking hot rods do exist.
There exist a few reasons, but a key reason is the related costs. A lot of those radical designs are equal parts functional, as almost every aspect of the design comes with a purpose-- be it side intakes designed to draw air into a rear mounted engine, or active aerodynamics designed to increase stability as speed increases. On some cars, even the side view mirrors serve the purpose of directing airflow to the cars engine. On an everyday daily driver, R&D like this would largely increase cost, for no real reason.
That’s not to say some car makes don’t try to borrow some of those design cues, as many of them do trickle down. Large colorful brake calipers and drilled brake discs, which serve no function on the street? Spoilers and non-functional vents or under-body rear diffusors? Staggered wheel setups, where the rear wheels are wider than the front? Increased wheel diameters with lower profile tires? More creative exhaust tip design, instead of just the regular exit from the muffler?
There is a long list of design cues which trickle down, but once they’ve reached the mainstream market, they largely go unnoticed (for example, look at tail/headlight design, and how radical they’ve both gotten since the 90s. Both now protrude and make all sorts of angles, aside from the boring “square”). Outside of this, a lot of the sacrifices in supercar design are just not practical for most peoples needs.
Take a look at the 2011 Kia Optima. While it’s certainly not a supercar, it’s certainly been injected with a good bit of “life” from the previous designer who did work for Aston Martin, if I recall correctly.
The supercar will always have its own presence, because it’s designed to evoke emotion and exclusivity. This is always evolving, so you can only copy it so much, before something else creative pops up.
I think it’s really a matter of utility trumping form. If you could shape a comfortable family car like something sexy it’d be trivially easy to supercharge or turbo an efficient engine and give it some extra kick. But there’s not enough of a market for that car. Generally, if you need 4 seats, spirited drives through the mountains are pretty low on your daily schedule.
Toyota tried to keep their MR2 line going until bagging it as recently as 2005. Looks a bit like a Porsche Boxster and costs half as much. And while I’ve heard nothing but “Yummy” about the Toyota’s performance, when you’ve decided to lay down a big lump of gold for a spyder, it makes sense to a lot of folks to go the rest of the way and get the status symbol.
My dad had one, the V6 version was pretty peppy, though I couldn’t get it to go a high top speed without the wind noise freaking me out. The rear window is vertical, and it felt like something bad was about to happen when you get over 90.
Anyway, the car was totally utility deficient. You can’t even go golfing with a buddy because there’s no room for two bags of clubs.
You have a sporty looking cheapo car, after the first 6 months, everybody will know it’s a cheapo car, so there’s no cool factor to it. Another 6 months later you’ll want to put a bag over your head when going out because everyone thinks you’re Midlife Crisis Man, who wants to look like he’s got a hot car, but can’t afford it. At which point, you’re borrowing your wife’s minivan half the time anyway because you can’t fit a blessed thing in the trunk.
Cheap cars have to be worthwhile on their own merit, not by parroting the design of an expensive car.
You might be right about the tax issue, but the term “highly aerodynamic” suggests that they are unusual in this regard. Most modern supercars are, in fact, just about as aerodynamic are most other modern cars.
The brand new Ferrari 458 Italia, for example, has a coefficient of drag (CD) of 0.33. That makes it slightly less aerodynamic than a 1998 Honda Civic (0.32) or a 1996 Buick Park Avenue (0.31). Some slightly older supercars, like the Lamborghini Countach, were actually notorious for their poor CD.
The Fiero was a success. It sold all it could build. GM was unhappy because it became a womans commuter car. For some reason they were not satisfied with that. It suffered a bit because of a tiny heating problem, they tended to burn.
Gm pepped them up (6 instead of 4) and put spoilers on them the last couple years. But the specter of a burning Fiero seemed to dampen enthusiasm.
You left out the word “yet.” 
Take an MX-5 (Miata in the US) for a test drive. I’m in the same situation as you - no kids, no need for backseat (my husband’s car has four doors, so it’s our ‘practical’ car) - and I bought one a bit under a year ago. I adore it; it’s as agile as a cat, accelerates like the proverbial bat out of hell when you ask it to, and is actually pretty reasonable on fuel economy. I couldn’t speak to US insurance since I’m in Australia, but I now pay about the same insurance on my MX-5 as I did for my little two-door Mazda2.
I know people bag it as a hairdresser’s car and all that, but honest to god, it’s the liveliest, most fun car I’ve ever driven.
F1 actually cars have a very high CD (up to .9 or 1 depending on configuration) and that is because they need to create a lot of downforce to improve cornering speed. Road-going supercars are similar (though to less extremes)
Hence the need for complex wings and body shapes (on both F1 and supercars) that maximise the required point downforces while minimising unnecessary drag elsewhere.
Those requirements dictate the form car will take and the skill required to perform that balancing act is massively expensive so you don’t do it if you don’t need to. At normal motorway speeds most of us are bothered more by wind noise and fuel consumption that downforce.
They are unusual. Aerodynamics takes into account a broad range of details, one of those being the amount of downforce produced, which assists in higher speed/cornering stability.
The CD is one aspect of aerodynamic design, but that same Italia is also producing many hundreds of pounds of downforce as speed increases, while we can’t say the same for the civic (neglecting the fact that it doesn’t produce the power to reach equivalent speeds). This is where the distinction is made, and it translates into real-world performance.
It also makes sense to highlight the fact that while great for a supercar, designed to overcome the air resistance at speeds, the drag created from more downforce also hampers gas mileage.
Harley Davidson makes fairly expensive motorcycles that are wildly popular. Many other companies have noticed this popularity and have produced motorcycles with similar styling, often to the point of having V-twin engines etc. There are perhaps a dozen such. Combined they have perhaps a third of Harley’s market. People who want a Harley, want a Harley because it is a Harley. They don’t want something that just looks like a Harley and says “I wanted a Harley, but this is all I can afford.”
Two words: Pontiac Fiero
It’s not just cars or bikes, all makers of expensive consumer durables want to have them perceived as desirable; rare; special; unattainable. Just ask deBeers about diamonds for example when cubic zirconium is just as good for most practical purposes.
However, the question does not necessarily concern plurals and in fact can read as a correct use of the apostrophes. And hence correct grammar.