Okay now I get it, so basically this Reddit karma is an Internet points that will help you become more prominent in the platform and like any other platform that has clout, you can use Reddit as a type of advertising for stuffs like almost anything, now I know the reason why some people are being ridiculed for farming Reddit Karma. Am I getting it right?
They won't necessarily be more prominent when they get more karma as goal is to unlock access to some subredits and to remove some account restrictions but with the rest you are right; as with any other platform, it can be used (and is used) to advertise business.
But as i said before, it's tricky to advertise there as spam content is removed fast, and even if it stays, other users can downote. Since reddit is very popular, I guess they try anyway.