The HTTP-protocol is (also) a de facto layer-4 transport-layer-protocol.
It might have been intended to be a layer-7 application-layer-protocol, but — look at how people are using it.
Applications are built on top of the HTTP-protocol somewhat similarly to how people decades ago would have built applications on top of the TCP-protocol.
Even the Fediverse uses the HTTP-protocol in this way — as a layer-4 transport-layer-protocol.