If they were called "tee rounds" or "tee triangles" or "tee ovals", I might have some issue with square shapes, but it seems to me that a box is usually a square or a rectangle, so that shape should almost always be preferred.
Terry, the Tee Box, I believe, originally referred to the box that held the sand that golfers used to make a little mound on which to place their ball to "tee off". Mission creep? BTW, could those little sand "tees" be the grandfather of topdressing?
I feel that, if all golf holes played straight and narrow, retalinear tees wouldn't appear as foreign to the landscape. but as fairways curve, dogleg or are wide enough to afford multiple targets/options, it gets harder to have a particular tee alignment be all things to all players. With multiple tees, on a bending fairway, each square tee has to be placed at a different angle. To me, this is visually distracting from the tees behind.
As with all things, Owners and Supts can have edicts with require retalinear tees. When this is the case, I have tried to even "hide" forward tee with slight bumps to reducce this .
As TOm D states, it can be hard to build retalinear tees of suficient size on cross-slope, evn more so when you have cross and dow/up slopes in tandem. Often times it takes a great deal of fill/earthwork to tie them into the surrounding area so they don't look like a series of package boxes.