I think the whole point of that part is that their relationship isn't just "cute" but serious and mature but not the focus of their life. They do it but it isn't important. The author probably wants to point that out about their relationship because if not I would feel they are very innocent with their relationship.
I think that's exactly what the author is going for and I prefer it this way.
In chapter 37 it's implied that they had sex (Miyamura's bite mark, both being naked on Hori's bed and Souta seeing them) but it's not shown
I don't know if I'm just missing some subtle references or sensei just decided not to draw anymore of those scenes but... it seems like Hori & Miyamura had sex once, and then never again lol.
Also, still waiting for the rest of the gang to find out about Miyamura's tattoos, that would be super interesting