Why is 2 boxing against the rules but PLing is allowed?

[Famous]

I am pretty new to this server, and have started a couple characters recently. I really like the fact that there is no 2 boxing allowed here, and agree completely with the idea that it has a negative impact on the community. One thing that has been really bothering me is the way that PLers conduct themselves in newbie zones. Where i get confused is when i see PLers take entire newbie zones to level up their paying customers. I really have a hard time understanding how this type of activity doesn't have the exact same negative implications on the servers community and player base as 2 boxing would.

A level 60 druid pulling the entire zone for their customer or friend has a far more significant impact than a boxed duo ever could in these zones. The only difference is that there are two people playing when PLing is going on, meanwhile an entire group or more of newbies is left with nothing to kill and a really bad taste in their mouths about this servers community.