Sure, but why does the Xbox One support it then, but not the PS5? And wouldn't it be possible to somehow incorporate the licensing cost in the console by means of a paid software upgrade (like on Windows) or a 'premium' version of the console that has it by default?

As far as I know Dolby Atmos can be seamlessly mapped onto to 5.1 or 7.1, so from the developer perspective there should be no effort/cost to provide Dolby Atmos audio. I might be wrong about this but I assume the licensing cost would be for the playback device and not for the 'right' to bundle an Atmos audio track with your game?

It shouldn't even be necessary. If you look at the DirectSound channel listing from ages and ages ago, I think even in Windows XP, there are height channels listed. But I've never seen a sound card that used them or let you select any higher than 7.1 in the Sound control panel.