I'd say it differs. First of all: you don't have to bike. We stil have cars. We have buses. We have trams. Etc. Thinking that you are left out of society if you don't bike is a very odd notion. Biking is simply nice and convenient.

In terms of accessibility the Netherlands is not as good as for example the USA is in some matters - their disability act is really great. Having said that: one benefit in Amsterdam is that it's a compact, walkable, bike-friendly city. And I reckon that often lends itself well to being disabled. You don't have to worry about driving somewhere, you can just walk (or roll) to the supermarket. But no personal experience!

For parents it differs what they do! Often they'll still have a car for some stuff (cars in general are common, just less necessary). But you can also put your kid on your bike with you, there are special bike seats for kids that you can put on your bike, very akin to a car seat. And bakfietsen (bin bikes) are very popular for parents with young children. You just put the kids in the bin. Kids also learn to bike from a young age.