Do you ever wonder why some players attack low-level characters? It's because they get tired of facing off against coordinated groups and multiboxers in battlegrounds. When that happens, they turn to world PvP instead. If you happen to cross paths with one of these players, you're likely to get taken out.

Places like the Tanaris camp and Stranglethorn Vale become PvP hotspots for level 80 players.

I'm in the same boat. Why would I bother joining random battlegrounds just to face premade groups and end up getting camped by them and their multiboxers? It doesn't make sense.

This is me in aquatic form, you cant catch me: https://www.youtube.com/watch?v=jAckVuEY_Rc
No, I don't wonder, because I know what the reasons are. Sure, some are like you say. But not everyone. I, personally, have ganked lowbies before. Usually because they're being terrible to someone else on my faction while they're trying to level, or I'm trying to get them to cry in guild or global so an 80 will come and fight me. Usually I'd win, and they'd bring more friends, and then I'd call my guild, and then we'd have some fun. But, those days are ancient history now.