That’s a good question! I know there is some cross play, but I think there are many titles that don’t have it. If you play multiplayer with friends who also have Xboxes, that’s probably a good argument to get one.
As far as I can tell, every game that’s listed as XBox exclusive on Google is available on PC Game Pass. I played Forza, Halo Infinite, Flight Sim, Sea of Thieves, Starfield, Ori, etc.
The last Xbox I had was the 360 so take this with a grain of salt, but they made the choice between XBone and PS5 so simple for me by making all XBox titles playable on PC. As someone who would entertain buying both consoles, I never found a compelling argument to bother.