I'm a smoker, so I always forget I'm wearing lipstick and then have a hooker cigarette butt. That gets a lot of the lipstick off.
Also, I usually eat before I put my makeup on - I have a fear of being a messy eater and I fear getting food or something on my freshly applied makeup - so I just put it all on afterwards.
IF I go out to eat and have lipstick on (I rarely eat out) then I don't, no. I just leave it on and reapply as needed. But I do wipe my mouth before re-applying.
Also - maybe it's just me, but I always apply lipbalm before lipstick. Even if it's all rubbed off - I still put lipbalm on before lipstick. My lips always seem to hurt if I don't have lipbalm on 99% of the time. :/