My guess is that the real reason is really simple. They don't want people to be able to escape ads anymore. They've done the math and decided that the revenue from ads is greater than the revenue from coins. Any time Reddit says "we're changing it because we have something better lined up" it actually means "we're killing this feature for good and we know everyone will stop talking about it in two weeks, so a lie of improvements is a good enough diversion". Fucking Reddit. Amiright?