Seems to me that dealing with the "disasters" that some people have dealt with when they did NOT wash their fabrics before cutting and sewing them is a whole lot MORE bother than washing them before cutting them.
It probably is true that MOST fabrics are well behaved - in my experience they are. But there are just enough of them that are stinkers to make it worth the effort to me.
I generally prefer to have my projects as simplified as possible. I don't like hassles. Glitches upset me. I feel that washing my fabrics does very much simplify things - in the long run -
Of course, I do miss out on the drama of wondering what changes may befall this project when it hits water for the first time.
And, if there are problems, I do miss out on the excitement of "will this unwanted color come out?" and "why did the seams come apart?" and how to fix the problem(s)