I havent seen a monitor (besides tvs) that has HDMI2.1 but not DP2.1

I can tell you mine does: a Corsair XENEON 27QHD240. Or the somewhat popular and badly named Acer Nitro XV275K P5biipruzx

I'd say it's usual for displays released 2-5 years old. HDMI 2.1 got somewhat quick monitor support for consoles, but search for "first DP2.1 monitor" gets results from 2024

And that parenthetical is exactly why people care.

TVs.