I have friends who say they do that. They find it romantic. If I am awake, and he is sleeping, I either wake him up in some nice way...kisses, caresses or other, or I try and go back to sleep a bit myself. I must admit, I don't watch him sleeping. (I do watch the dogs sometimes, if they are dreaming...but that's another story).
SO..are you a "watcher"? Why?