Minecraft is incredibly popular and it's normal to run your own server. (It's the 5th most-watched game on Twitch; at 81,000,000 hours per month!) I don't play, so I can't authoritatively say there is no company that provides "default" servers that new clients log into, but I've never heard of such a thing.

(If you look at the other popular games on Twitch, they all provide servers and can't self host. GTA V, Fortnite, LoL, CoD, Valorant, etc. So there is no market for anything but Minecraft-related services.)

If you do the development work to support hot protocol of the moment X, chances are in 18 months nobody cares because either (a) now X is old news and nobody uses that any more or (b) X+1 came out, it's incompatible and you'd have to do the work again for it to be useful.

If an enterprise customer will pay $$$ to support X this can still make financial sense, but Cloudflare's non-enterprise customers aren't paying $$$.

Minecraft is apparently not going anywhere, it's still very popular a decade after release. And my understanding is that the protocol is fundamentally the same as ever. So, you do that work once, and then you've got a free proof of concept apparently forever.

There's a reasonable amount of servers with the traffic to need to worry about ddos attacks, and have revenue models from selling ingame perks (often in ways forbidden by the minecraft ToS, but that's relatively toothless for these servers) that would allow them to pay for this service.