Ok, not ALL new motorcycles, but all sport bikes and all “naked bikes,” I.E. no plastics over the engine and parts, have that “splashy flashy” design. You know what I mean. The hump-back gas tank, and the tail pointed skywards, and the pipe sticking out of the back: view this Honda 919. If I want a new Japanese motorbike, why must I have that “sporty” look? I prefer the older (80’s and before) look, like this CB-750. Why don’t they make it in the old style anymore?
Styles change. It’s the same with cars, clothes, bicycles, houses, you name it. If you wait long enough the old style might come back as a “retro” style.
Man, I’m just waitin’ for a bike with tail fins. Remember those?
Once upon a time, there were just “motorcycles”. If you wanted a dirt bike, you modified a “motorcycle”. In 1969 Honda came out with the CB750. From then into the late-1970s there was the “UJM” (Universal Japanese Motorcycle) that pretty much looked the same from company to company (HYKS – Honda, Yamaha, Kawasaki, Suzuki). But by the time I got my first bike, there were already specialised bikes coming out. “Enduros” were built on lighter frames and offered two-stroke engines (more power for the weight/displacement of the engine). My first bike, a Yamaha LT-2 Enduro, came in two flavours: MX and Enduro. The Enduro was street legal, while the MX had no lights. So in the 1970s there were “street bikes”, and there were “dirt bikes” (which may or may not have been street legal). That stayed pretty much the same into the 1980s.
In about 1986 we started getting the “sport bikes”. The first one I remember was the Yamaha FZ-600. About the same time we got Katanas and Ninjas. People no longer had to “hot rod” their Standards (i.e., “standard class” motorcycles) for racing. And then there were the cruisers. No need to “chop” your standard, because Harleyesque “cruisers” were being made. And people seemed to gravitate toward niches. Why make an “Enduro”, when people just want to ride in the dirt? “Dual sports” were still around, but as I recall they were rather anemic compared to my Enduros I had as a kid.
So over the last 20 or 30 years, motorcycles have become more specialised. HYKS discovered that people wanted cruisers, or they wanted sport bikes, or they wanted dirt bikes. Boring old standards no longer earned their keep.
I’d thought that the CB750 was still being made as the Nighthawk. I checked, and all I found was the CB250. Triumph still makes a standard; it’s liquid-cooled now though. Royal Enfield has been making the same standard-class bike since the 1950s. Some BMWs might qualify as well. The choices seem to be few, but there are still a couple out there.
But it’s all a matter of personal preference and profit margin. People want cruisers so they can pretend to be “bad boys”. People (like me) want sport bikes because they like going fast. Others like to ride long distances, so they buy tourers. And people want the most capable bikes they can get for offroad. There just doesn’t seem to be much interest in standards. Standards don’e have the power of sport bikes, the comfort of tourers, the image of cruisers, or anything near the offroad capabilities of dirt bikes. People don’t want bikes that do everything competently; they want bikes that do “their thing” very well. So they tend not to buy standards.
Me? I love standards. I’d have a stableful if I had a stable and the money to buy them. But I like to go fast, so my “one bike” is the R-1. (I still have my standard-class XJ600 Seca II though. 
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