I’ve been known to look at yarn on eBay. (Pause for laughter to die down.)
Sometimes you see recycled yarn for sale there, the kind of yarn where a seller has unraveled a commercial sweater. These vendors usually do not wash or otherwise straighten the yarn. They say it will work just fine to knit the yarn as is.
When I rip out my own knitting, I almost always wash it and let it hang in a pretty damp state. The weight of the water in the yarn works to straighten the yarn as it dries.