You get some secret powers like flagging, downvoting, and the ability to initiate polls. But mainly it's a vanity metric.
By the way I had the exact same experience, and most submissions I make die with 1 or 2 points even after several years. Then other times I'll get hundreds of points for some whimsical thing that I didn't think was important at all. I rarely pay attention to people's karma scores unless I think they're whoring for points, like persistently making 'me too' posts on popular issues or posting every single thing from a popular blog.
Just post what you think is interesting, think your opinions through before expressing them, don't be afraid to say that you were wrong or have changed your mind even if you feel momentarily foolish. Same as life really.