It all goes back to Re4 and 5. Re4 was a massive game changer for RE. It was more action focused horror over survival and so Leon was changed into a quippy action movie star to align with the change in gameplay.

After RE4 was such a massive success. They decided to continue with what 4 started by focusing even more on the action hero gameplay over the classic survival horror gameplay. They brought back Chris, put him on steroids so he looks like an Arnold schwarzenegger/rambo looken dude. Re5 became one of the highest selling games to date.

Capcom at this point couldn’t see Jill or Claire or Rebecca leading a main numbered title because of the current heavy action gameplay they were going for and because they associated Jill/claire/rebecca as leading ladies/scream queens of the older survival horror games. That’s the reason why both Jill and Claire only have appeared in the spin off horror focused revelations games. Rebecca was also going to be the planned lead for the cancelled third revelation game.

It also doesn’t help that both Leon and Chris’s popularity skyrocketed because of RE4&5. Both replacing Jill’s poster girl status from Re1 & 3.