Honestly the reason to use such a service in lieu of owning a car is a combination of the day-to-day lack of need to own a car based on how one lives and wants to live, not having a safe, reliable place to store a car when not using it, and the general expenses of owning a car over the term.
In the country or the suburbs, one's day-to-day life might well require using a car if one is going to be able to really go anywhere, at least in a reasonable amount of time. Likewise one might well have plenty of space in which to park said car. And even if one's life may not require it, the time saved driving versus walking or biking (particularly in inclement weather) might simply make the convenience of a personal car a lot more important. It's not pleasant if going to do a fifteen minute task takes an hour when driving there and back would make it take a total of twenty minutes.
I'd actually expect in some ways that it could be easier in the countryside, if one's village is walkable in ten minutes, and if the mass-transit to leave one's village takes one to useful places quickly. If the village is too spread out to be easily walked or if the mass-transit takes too long to travel to other places one might need to regularly go, it would be difficult to not use private transport if one doesn't want to be essentially homebound. If the village is small enough then it might not be worth the company's time to place a rental in town if it simply won't be used enough.