Once I started playing Chess with a clock, I find it hard to play without one for two reasons.
1) It gives a DEFINITIVE END to the game. -- If I have like 15 minutes, I just set the time controls to like Game/5 so the game will last only 10 minutes at most.
2) It helps to show who's turn it is. -- With a clock, I know who's turn it is by a raised button... even if I'm not paying attention to the move or had to leave the table for some reason (use the restroom or grab a snack / drink in CASUAL PLAY. I don't leave the table in the middle of a game in Tournament Play). This also helps to enforce the "Clock Play" rule, as I'm not required to move until my clock is running.
With a clock, the enforcement of the Touch Rule (which I refer to as "Touch Move") is based on the time controls. In Blitz games or faster (Time controls under Game/15), I won't enforce it because the game is moving a bit too fast for traditions.
For Speed games (Time control between Game/15 to Game/30), I encourage Touch Move as the game is running a bit slower, but I won't enforce it unless it's a Standard game (Game/30 or longer) where all the traditions of the game should be observed.
This is just my 2 KB here.