Taxis are ridiculously expensive. I use IGo, and have a $15 a month membership whereby the first 3 hours of the month are “free” (aka, the first three hours of the month are $5/hour). I will definitely use at least 3 hours a month, and there are many months where that’s all I need – one big trip to run errands like taking the recycling to the drop-off point, go to one store for TP and household things, go to another store for groceries, go to the bakery, all of which is a hell of a lot easier to do if I can carry things in a car than if I have to carry tons of stuff on a bus (or more precisely, many buses, which is a pain in the ass to lift stuff in, lift stuff out, and try to find a place to put all the stuff while riding where it’s out of the way of other riders… I only have one lap).
Rental cars can be cheaper on weekends, if you’re renting for a full day or more. But they’re most definitely not cheap at all during the week. It’s ridiculous how much they wanted to charge me, and then I’d have to either go farther out of my way to pick the car up, or wait on them (and having been down that road before, they’re not necessarily very prompt when picking you up… they were over an hour later than we requested, even after calling them repeatedly asking where they were and when they’d get here, because they’d scheduled too few people to handle the load, knew that, and didn’t bother to mention it when we first requested the pick-up days earlier). I’d also have to pay for gas plus insurance, since I have no car insurance that would cover a rental, not having a car. My one long weekday trip, I looked at a rental, and at best it wouldn’t be any cheaper, at worst the gas would cost me at least an extra $40 than just getting the day rate at IGo (which is conveniently cheaper during the week than on weekends).
So, short answer – I use a car little enough and often enough that this is the cheapest and most practical option. It’s MUCH less money than owning a car, even if it’s paid in full. I pay less than half in fees than I did on insurance, gas, registration, and maintenance, even on an old car that cost very little to insure. Taxis… anyplace that’s far enough to drive instead of walk/take the bus, it’s going to be at least $30 for the trip (a five-minute trip costs $8 or more, and we’re talking about at least 20 minutes each way, in traffic, and that assumes you only have one destination), and you have to wait for the cab to show up both going there and coming home. I have 3 IGO lots with a total of 6 cars within a 10 minute walk of my apartment. And reservations are simple: you don’t just walk to the lot and hope there’s a car there (you wouldn’t be allowed to take it even if there were), you go online, see what’s available, and reserve a specific car for the day, time, and length of time that you need it. I’ve had to go to the next farther lot (like, maybe .1 mile farther and still within a 10 minute walk) maybe two or three times since I started my membership over two years ago. The cars are also cheaper to reserve on off-peak hours (like weekday afternoons), so I often take advantage of that, too, if there’s a given month where I need more than one big trip.
I rarely leave the city, and if I do it’s pretty much always carpooling with someone who owns a car. All I need it for is basic errands, and for that it works really well.
I don’t know about other organizations, but with IGo you can’t just “rent” a car unless you’re a member (although I think there are some agreements in place with car-shares in other cities to allow those members to use our cars), so it’s not aimed at tourists wanting to tour around a city.
They’re even starting programs where someone can get paid for sharing their personal car. Almost makes me wish I owned one again – it might offset the costs enough to be worth it.