Is so funny, this weekend I bought two fat quarters. One was "standard" that is with the selvedge. The other had the selvedges cut off, of course it was fabric I wanted to know more about! Since I recognize and follow fabrics around, I know some of the fabrics in fat quarters were from name brands a year or two before and those will often be deliberately cut off.
Hint: Typically the fat quarters sold rolled up at Joann are a higher quality than the flat folded craft fabric often found in the seasonally/color rotating ones. Likewise, among the fat quarters and other precuts at Walmart, you can find some quality pieces of fabric. I think some of those, particularly by Wamsutta are left overs from commercial projects.