When websites fail, it isn’t because people are dumb—not smart enough—or lazy.
As I and others have said before, people aren’t doing progressive enhancement because it is harder than not doing it.
‘Hard’ in this context isn’t a measure of how much intelligence or skill is required to solve the problem. ‘Hard’ here is a description of the volume of effort required, namely that it’s more than you would have otherwise needed to make a passable website.
It’s the system that guides the effort and controls which problems are worth expending that effort on.