Is it urbanisation? I've noticed this trend in the suburbs in my country too and there seem to be a couple of reasons:
1. Driving tests have gotten progressively more difficult and more complex over the last 10-20 years.
2. The cost of learning to drive is insane and getting more expensive.
Personally, I put off learning to drive and now that I'm in my 30's I'm finding it very hard to justify the cost and time investment necessary, despite wanting to get a license. Until I need it, I think I'll continue putting it off.