Being able to DIY seems to be a mixture of opportunity and necessity. If more people are renting, their landlords carry more of the responsibility to repair, and wouldn't want their tenants to do work for possibly a few reasons.
I also think having more disposable income, coupled with an attitude of everything needing an expert may discourage people from trying. And, it seemed the DIY market became saturated. People would have to change their paint/tile/cupboards, etc quite frequently to keep all those retail outlets going.
Home or vehicle repair does not come naturally to me, but when I wanted to work on a ranch I figured out how to do many things in order to get my paycheck. I'm female, and wasn't around anyone with skills when growing up. Now, I even moonlight in the winter remodeling rentals for friends just for fun.