In one of Robert "Uncle Bob" Martin presentation you may find the answer. The number of developers duplicates each 5 years. That means that any point in time half of the developers have less than 5 years of experience. Add to that realization the fact that inexperienced developers are learning from other inexperienced developers and you get the answer on why we repeat the same mistakes again and again.

I guess that is a matter of time that the reality changes, we will not duplicate the number of developers indefinitely and experience and good practices will accumulate.

Taking into account the circumstances, we are not doing so badly.