The effect of this may be that people who genuinely want to play do not know how to seek opportunities effectively. A related problem is that some organizations which ideally should be assisting such people do not do so. We can only speculate on the reasons. Sometimes finances are a major concern. Some of the reasons may be sociological.
Many people simply feel most comfortable when surrounded by people like themselves.
Much of the early music movement in its beginnings involved amateur groups which were small, cohesive and, regrettably, sometimes more socially than musically oriented. Good material on early brass, double reeds and percussion is not lacking.