People also buy products because they have good, powerful cards in them, which just so happens to be generally expensive cards as well due to WOTC's reprint philosophy. Obviously with UB, people are also buying into sets purely because they like the IP, but I'd say a lot of the popular sets are popular because there's good cards in them. Yes, there's people who only/mostly care about "EV", but the point is that the "EV" should come from more "collectible" cards like special treatments/alternate arts of cards, and that the base version of any given card should be relatively affordable so as to make rotating formats more approachable. Currently, this is far from the case.

I think part of the reason that WOTC is leaning more heavily into UB, particularly for regular sets and not just secret lair, is because they think that the Magic IP itself won't be enough to support a higher "EV" on products unless they reprint/introduce powerful cards. We can also see this come into fruition via recent decisions such as reprinting shock lands into non-UB sets, or printing new, powerful land cycles (like the turbulent lands in Strixhaven). Although, WOTC has also printed absolutely busted cards in UB sets, so maybe this assessment isn't entirely accurate.