Most useful quilts are not square, I don't think.
Comforters are usually square, but I like a quilt to be rectangular for a bed so I can flip the top up over the pillows.
But my wallhangings and just-for-fun quilts afre, indeed, usually square noq you mention it.
Minis are usually rectangular if they are intended to mimic a real bedquilt.
That's just me, of course.