Is it easier to block DDoS attacks to a HTTP service than a custom service on tcp/udp ?

I have a small game server that's getting DDoSed by an angry player, we managed to block it by moving over to OVH but the thing I found really weird is the fact there were so many free/low cost services to block DDoS attacks on HTTP based services but whenever you wanted to secure a service running on some arbitrary tcp/udp port it was always more expensive or wasn't even available.

Is there a reason for this?

I thought since HTTP runs on TCP the same DDoS mitigation techniques ISPs apply will work for any service running on any TCP port.