I used to be diligent and washed everything. Then I got lazy and didn't BUT I made sure that ALL fabric in the quilt was either washed or not. By now, I have no idea what was washed and what wasn't. I use it as is and wash the quilt with color catchers.
One thing I NEVER prewash is precuts. One fabric I tend to still wash is batiks.
As for the crinkled look - I still get that even with prewashed fabric. It's all fun and games and fortunately, I am not allergic to chemicals. Now show me a blooming tree and I'm a snarling mess.