A reason was backwards compatibility, studios were already putting lots of money into PS4 and XBox One, thus PS5 and XBox X|S (two additional SKUs), were already too much.

Don't forget one reason that studios tend to favour consoles has been regular hardware, and that is no longer the case.

When middleware starts to be the option, it is relatively hard to have game features that are hardware specific.

Games budgets ballooned and it was not longer financially viable for single platform games.