This is a self-fulfilling prophecy. Someone tries to write an analysis routine in 3.x, but then is quickly told "nobody in science uses 3.x, because of <vague

This is a self-fulfilling prophecy. Someone tries to write an analysis routine in 3.x, but then is quickly told "nobody in science uses 3.x, because of <vague reasons>". Result: everyone sticks to 2.7, so nobody ever even tries to build against 3.x when writing packages.