Years ago this was a common practice, but now you don't see this too often. I am with you...I want my fabric cut, not torn.
When I lived in Denver, one of the quilt shops I shopped at always wanted to tear the fabric. I asked them nicely to cut my fabric. The saleswoman tried to convince me that I would be able to see the grain line if she tore it, but I still asked her to cut the fabric.
Some may disagree with me, but I think tearing the fabric puts undue stress of the fibers, and you can lose and inch or two in length.