It doesn’t matter too much because existing consensus rules already allow spam. It would take a consensus change (rather than just node-relay behavior) to truly limit spam that people are willing to pay for, which is unlikely to get broad enough support. I would not support consensus changes to allow or incentivize more spam. Such a stance can only be supported if one is long-term bearish on monetary/settlement demand.

There's an argument but it's probably not a good one. If demand for blockspace doesn't pick up before we've had a few more halving and/or the price appreciation slows down significantly, we could have a situation where miners can't afford to sustain the high levels of hash power they have invested so much into producing. They might look for ways to increase fees by facilitating more data storage applications, but it really doesn't seem like there's much demand so it probably wouldn't do much. Thankfully the difficulty adjustment will keep the mining industry from collapsing completely, but we could see a washing out of less efficient operations and some consolidation and centralization as a result. Not sure if any of that is likely to happen or not. I think fees will pick up the slack for lower coinbase rewards by then.