One Pocket 'cause:
1,2,3,4,5 rail banks
1,2,3,4,5 rail kicks
nasty safeties that make people squirm worse than ball in hand in 9-ball
the ability to challenge your opponent with various degrees of penalties
you must know when its best to play safe versus shoot
intentional scratches without ball-in-hand
a little less luck than in the other games
you can stall
double kiss safeties and banks
tickys
caroms
english banks
force-follow hug-the-rail shots
freezing a guy on the rail 10 times in 15 minutes
having someone study the lay of the balls for a few minutes and exclaim, I'm f***ed!