Quite common. I guess there may be two reasons - there are more vents on the drivers side, and also possibly the drivers side is a bit warmer due to his/her presence.
On a humorous note one may blame it on Murphy - the LH side needs one moves across to wipe it.
I had a similar problem, with only the left side front window getting misty with the AC on. I realised, most of my friends who sit in the passenger seat, tend to move the vents towards the window so as to not blow the cold air straight onto their body. I just point the vents in and downwards and the problem gets solved.