That’s primarily because of two things:I don't mean they refuse to show show gay scenes but they are normally for shock value, which is the scene you're referring to. All the other scenes of sexual encounters between men are either just hinted at or cut altogether.
Homelander/Soldier Boy being one and Homelander & Doppelganger Homelander being another. In the comics Homelander kills doppelganger after having sex with him whereas here its hinted at then he's killed.
I may be wrong but think that if was woman on woman they would show the sex scenes before going on to do the shock and gore
1) the actors refused to do the scene because they thought being in a gay scene could damage their career/image (fragile masculinity )
2) male gays sex scenes are more difficult to sell to white male audiences, as they find this either degrading or obscene. Female gay scenes are more marketable for that audience though and that’s why we got so much of Queen Maeve lesbian life last season. In many ways, Amazon Prime and almost all companies act the same way as Vought in The Boys’ universe. They just care about what’s marketable. That’s both funny that they understand this issue on the show, but also sad, as they won’t be brave enough to challenge these ideas for the sake of views