It's just that there are more people in cheap gear than there are leechers. Why punish those who are innocent? Also, this leads to tincans having an even harder time earning back their money.
Also, I'd like to argue that for leechers to vanish the benefits should be smaller for leeching than for playing normally. If they earn as much as a normal guy that plays the game, they'll still leech. They must earn stuff slower than regular players for their amount to reduce. I don't know how this can be done.
And you're argument that it doesn't matter much if you have to pay a little extra. I still say it doesn't matter much to leechers either.
The leechers will just be harder to spot since they're all in some form of gear that's just above your magical "below this you still have to pay"-line.
This will make leeching slower. And playing like it's meant to be played slower.