I used to set transient-mark-mode to t myself. But being able to set a mark and use C-xC-x to switch the cursor and the mark point is too powerful. It allows you to set a mark, go edit something else, and then go back to where you were.
Granted, you could probably do that with transient mark mode, but seeing everything highlighted would be too annoying.
You can do the same thing with bm.el, but you also get multiple bookmarks (visible in the buffer) which you can then cycle through. I find it helpful to have bookmarks and the region decoupled.
Granted, you could probably do that with transient mark mode, but seeing everything highlighted would be too annoying.