I've always rotated the camera, and when I used to stream people would complain about it all the time.
Streamers and casters stick with the standard because it keeps things consistent across different maps and spawns. I'd bet more people actually rotate the camera when they are playing in private, you just don't see it.
For me atleast it has always been about pushing towards the enemy. It feels a lot more natural to me to be making forward progress across the map. In CoH it also makes it much easier to put your units into cover, which is usually facing the enemy.
This was the point I was trying to make. Sometimes it is difficult to get them to move to the right spot, and sometimes they will vault, which is usually disastrous. My gameplay is too cringeworthy to stream so I don't worry about rotating. There are a few maps that have problems when rotating. Lienne can sometimes cause problems - particularly in giving garrison commands to the last building in a row, if you rotate the view so it is straight on to the opposing team.