Maybe most smaller ones have hosted both things separately, e.g… with a dedicated minecraft server hoster and a common website-building+hosting service, and don’t want to run an extra server for a proxy just for this.
With bigger servers (eg. Hypixel, 2b2t) or selfhosted servers (eg. mine), everything is on the same physical (or virtual) machine anyway and therefore everything has the same address, so you wouldn’t even need a proxy.
Maybe most smaller ones have hosted both things separately, e.g… with a dedicated minecraft server hoster and a common website-building+hosting service, and don’t want to run an extra server for a proxy just for this.
With bigger servers (eg. Hypixel, 2b2t) or selfhosted servers (eg. mine), everything is on the same physical (or virtual) machine anyway and therefore everything has the same address, so you wouldn’t even need a proxy.