I would also wager that potential repeat customers eventually just bought their own scooter. It's not like they're particularly expensive. If you really enjoyed using one of these, why rent? (I know there are reasons, e.g. I wouldn't want one of those batteries in my house at all. But my point is simply that they can be inexpensive, especially compared to the price of renting.)
For me, the biggest advantages are having one around whenever I need it, even if I didn't plan for it, and being able to leave one out of the way anywhere and not have to worry about using it to get home (might prefer a walk), or it getting stolen. It would absolutely be cheaper to buy one of my own, likely several times over by now. I'm mostly paying for the convenience.