I bought fat quarters, then I realized I could make just 6 for the set with them. So I went and bought more of the same fabric so I could make an extra block for myself to keep. So I have blocks for myself that match the sets I mailed. I sure don't want to mail 5 blocks from my 5 sets just to receive them back again!
It's handy to buy fat quarters for this particular block because the size fits nicely to the pattern. Maybe it could be considered for a set to be 5 blocks instead of 6. That way if people enjoy using fat quarters they would have enough fabric to keep a block for themselves. A lot of online fabrics are sold in FQs or bundles of FQs and it's a nice way to get a broader selection of prints than you might buy otherwise.