To sum:
- Getting PLed will not happen all the time, it's rigorous, tedious, and mind numbing for the person giving.
- It helps get your friends to higher level so that you can play and enjoy this game with them.
- It will most likely not be exploited due to facet number one, and if it is botted, SE will deal with that idea.
- It benefits the PL as well as those being PLed by giving minor amounts of exp (I gained 2 levels on my level 33 THM PLing my friends)
- It helps mentor new people in the game with a veteran who might share some knowledge with them while PLing (ie. this aggros, that doesn't, suggestions for party places when the PL session is over etc.) **this depends on the person, but I have found most people to be helpful**