Really? The last time I rented a car in MIA, I showed up, was Enterprise Executive so I went and could choose any of a few dozen cars that had the keys already in the ignition. After that, I drove up to the exit at which point the person pulled up my reservation, scanned the car, and gave me the paperwork. I was out in less than 5 minutes from when I chose the car.
Return was just as easy, just pulled into the lot, someone scanned the car and sent me on my way.
Granted, it's not as easy as RFID and go, and I don't have that much experience with rentals because I don't use them often, but I wouldn't call it "far more" of a hassle, at least in my limited experience.
That's how bigger airport car rentals work, you've obviously never rented a car outside an airport location. Non airport car rental locations usually take a lot longer to go through the whole process, no streamlined/staffless way to rent, and have limited hours and a much smaller staff. I think the one by my house is even closed on Sundays. If you have some jackoff in front of you who is fighting with the staff about being turned away for not having a credit card you end up having to wait for the staff to deal with that before they can process your rental[1]. I've also had to wait for the car to be cleaned in the past when they got unexpectedly busy.
On top of that airports are usually not located near where people live. The vast majority of people renting a Zipcar for a day trip are not going to want to go to an airport to pick up their car.
Airport rentals can get significantly backed up during busy times. I've gotten totally gridlocked in the rental car parking lot before.
[1] actually happened to me
I don't have a car right now... and while I haven't rented a car lately, (I'm willing to pay extra for uber/lyft as it means I don't have to drive or deal with parking) I do pretty regularly rent a uhaul van, as the on demand hauling solutions are less convenient and/or more expensive, in my opinion.
The uhaul process is app-based and can be done at the last minute with your cellphone. They do want a cellphone photo of you and of your license, which is then verified quite slowly, but I don't have to personally interact with any humans to get my uhaul van, and it's usually pretty quick.
Where ZipCar excelled (I haven’t used it for a number of years) was being able to not own a car and effortlessly get one for an errand or quick trip.
These days I rent far more often, and even being part of elite programs and being very experienced with the process it is still far more of a hassle than simply approaching a car you’ve booked online, tapping your RFID card and driving away.
I think ZipCar theoretically still has utility for that type of use-case.
A big drawback also was the inability to select a one-way trip. Sometimes you want to get somewhere and stay for a while, and it’s simply not cost-effective (or efficient) to tie up a car for 3 or 8 hours vs. just driving there.
I believe this is a use case that Car2Go addresses, although I haven’t yet used that.