I think the problem is that to learn to make simple things you first need to learn making complicated things. This is my story and pretty much the story of every person I ever talked to that learned to make simple things. Some people get it faster, some get slower and some never learn to appreciate simplicity, but everybody first had to learn to make before they learned to make simple.
So now realise we were through decades of exponential growth of the number of developers and at any point in time people with experience were greatly outnumbered by people with little experience and the answer becomes easier to formulate.
Simplicity isn't something that is easy to teach. The best ways to do it I found is by mentoring and working with people, but there are so many people you can meaningfully mentor on a daily basis. People with experience are so outnumbered (and also promoted up if they are any good) that it is very hard for an average apprentice programmer Joe to be able to find his master.