I can't even imagine people closer to tropical climates trying to ride bikes anytime except winter.
Also gaining in popularity recently is the so-called "Duofiets", which is a two-person side-by-side tricycle, which lets people without a disability help out. Here's a video of a project that combines student housing with elderly care (also an interesting project in itself) that shows off the bike halfway. My grandma was taken on daytrips with such a bike in the last years of her life, and it really brightened her day.
Hase Bikes in Germany build a wonderful range of adapted bicycles and tricycles that can accommodate almost any disability. If you're capable of moving your arms or legs, there's a cycle that will work for you.
If you meant to ask "What about people that physically can't ever bike (but can drive)?"
What percentage of the population, honestly, do you think that is? Out of shape people can lose weight and eventually learn to bike. Very few people can-drive-but-not-bike, and surely exceptions can be made for them.
I remember being impressed by the fact that while this guy had so much trouble bending down, he was riding a (regular) bike.
I've also seen 'seriously' pregnant women bike around, men/women with a kid strapped to the front and back of the bike, with sometimes a third kid in a kart behind the bike. I also regularly see groups of elderly people on sports bikes (often with some electrical help though), as well as really young children.
There are plenty of people who really can't ride bikes, but probably far fewer than people from non-biking places assume.