Yes, but if it's your goal to have fewer cars, then you'd make an effort not to need to use it at the same time. If that's not what you're trying to do, fine. My wife and I share a car. It's slightly inconvenient sometimes, but really not bad at all. For our particular life anyway.
So here we're talking about iPads. Some families need multiple devices for various reasons. Some don't except for the fact that iPads don't support accounts. No one's saying you would have to use them. But you're not allowed to.
I held off a while on giving my youngest child his own iPad because he and his brother were playing nicely together on one more often than not. It turned iPad time into social play-together time.
Remember, we're comparing to iPads. Apple intentionally hobbles them to induce demand for multiple iPads. This isn't a question of being allowed to own multiple iPads/cars. It's a question of being artificially prevented from owning a single one.
The point isn't that you have to commit to being a single-car household for life. It's that at some points in time, you can be.
How many TVs do you have in your living area?