Thing is that everyone is a creator and they can profit regardless of content quality.

Imagine Bob. Bob doesn't care about Steem as a platform.
Bob post some spamy content 10x / day.
Bob don't need to compete with you with quality content. He doesn't have to sing. He doesn't have to do anything. He can just selfvote.
There's also Charlie, he has a lot of SP, and he wants to earn somehow. Easiest way? Upvote himself. But it's not really publicly acceptable. So Charlie can sell his votes to someone. Bob will buy it and upvote himself.
Dave is a good guy, Dave curates quality content, but can't earn as much as Charlie or Bob. Dave doesn't like spam, so he would downvote Bob posts, but then, Dave would have to spent his VP on that instead of curating quality contet. He would earn less on curation. Charlie get his money anyway. If Bob will be continuously downvoted, he will shift to some other accounts,after all he doesn't care about ontent or audience so using multiple accounts posting whatever doesn't change anything. He buy votes, he profits. Dave can try to fight it but it's not easy to spot abuse, and fighting it means losing.
Eve creates quality content, sometimes curates quality content. Eve has some friends that like her content but they already sold most of their SP to voting services. Even Charlie likes her content but it's far less profitable for him to vote than to just sell it to Bob.

EIP is aimed at changing that sad image.

Bob would no longer earn that easily, so will not buy from Charlie at that price, unless he promise to share with curation reward... but then it would have to be some others voting. But why would they vote for Bob's spamy content instead of looking for better curation opportunities? Dave could downvote abuse without being forced to sacrifice his curation efforts. Charlie would rather vote for Eve content because it's good, so there's pretty good chance for decent curation rewards.