I regularly use Graviton CPUs on AWS (even if Amazon pays the cheaper ARM license), why would people switch back from that? It's effectively better in terms of performance/price, I expect these improvements to slowly but steadily reach the on-premises world as well.

Yeah, but everything on AWS is already way more expensive than it should be, so the slight discount on ARM instances is a gimmick from Amazon to diversify their servers or something. Actual ARM servers aren't cheaper or better.

The latest figures sugegsted that about 50% of server shipments into the clouds now are Arm.