I always offer to pack a bowl or roll a J when others are around. Its just a sign of curtesy in my book.

Now of course, if they are being dicks about it, or refusing to let you pack or light or anything, then yeah, thats something I would take offense to as well.

I think the only time I have ever lit a bowl for someone was when they were new to smoking and using my bong, which confuses the hell out of them, or if they dont have their hands free but want to take a hit still. Then I have been known to light the bowl, and pull the slide/let the carb go for them, so that they dont have to stop what they are doing in order to smoke.