I always think of it like performing. There are those who perform on stage and love the adulation of the crowd and then those who perform on reddit and love the adulation of the other redditors. In that sense, it isn't really meaningless, but an acknowledgement of you being interesting or having interesting things to say. The problem is that people start to get obsessed with it and forget about the original purpose and find that the easiest way to get karma is through cheap, rehashed material. Think of it like comedy. You have many comics working on material and trying hard to gain an audience and then you have people like Carlos Mencia who just steal other people's material for the easy laughs.

Anyway, I do like your post, but I will support your cause against karma by downvoting you.