Natural incentives may eliminate the addition of new layers of it in time.

They will never remove the scar tissue that has already accumulated.

The chain will grow in time, but then, so does hard drive space and processing power. Spam pulls that growth forward, putting node ownership less in reach today.

Besides, we know we can't stop the spam. Just like nobody can stop the email spam. But that doesn't mean we need to assist in delivering it.

And of course, there's the bigger matter: the Core team is releasing a version of Bitcoin that involves less choice for the person running the node. Knots allows users to relay, or not relay, what they choose, with greater granularity. It's the same a the choice between decent operating systems and Apple operating systems.