I live in a small village, about 8 miles from civilisation, and invariably cycle into town, regardless of weather. Indeed, there is a surprising hardcore in the village who do, which is gratifying. Sure, there are disabled folk and the elderly, but the clear majority, an easy 95% or more without any shadow of a doubt, are healthy and able to do the same, but choose not to for no other reason than they are...
Bone idle lazy.
They'll come out with all sorts of reasons to justify it, but they're all excuses. Laziness and the desire to avoid expending physical effort is the problem. Until society acknowledges that nothing will change. Sea levels will rise and be lapping at their doorsteps and they'd still rather drive than walk the kids 400 metres to school.
It doesn't help that there is is culture of machismo that views cars as sexy objects of desire, or those who - unwittingly or otherwise - use cars as a means to express their perceived social station, which serves to not only legitimise but actually promote car ownership and frivolous use thereof.