I'm a washer. I wash precuts in the sink, then spin in the salad spinner (although I must say I don't buy many pre cuts).
For me, pre washing is a genetic characteristic. My mom pre washed everything, so I do too. I have found that everything seems to shrink selvedge to selvedge. Moda, Hoffman, Kaufman, etc. everything except batiks (and they bleed). It's my understanding that the fibers don't really shrink, but they were stretched during the printing process and the washing relaxes them back to their original length.
As far as the non washers not having problems, I think it's two reasons: Cotton batting and/or quilting stitch stabilization. If you use cotton batting and don't pre wash the batting, it shrinks giving you that crinkled look, so any additional fabric shrinkage absorbed. Also, the closer together your quilting pattern, the more the fabric is stablized, again minimizing shrinkage.
So do I really, really need to pre wash, probably not. Will I continue? Yes. I can hear my mom's voice. I will also button my coat, and not race my sewing machine.
YES!!! you need to buy an accucut!!!