FF14 player count reached the lowest point in 4 years. We lost 75% of the playerbase.

[BigCheez]

I'd suppose the drop to be more because Steam players can only play one game at a time through the Steam interface, and a lot of interesting single-player games came out over the last six months.

How does this differ from other platforms?

This here is one reason why I'd vouch that the Steam playerbase has a slight demographic difference from the rest of the PC playerbase. I don't play on my PC via Steam and I usually only play one game at a time, period. I am not constantly being tempted by other video games. If I do get a new release, it's going to be on my PS5, and I'll disappear for a few weeks to play it before returning to FFXIV. (I still need to finish out achievements in Rebirth.)

People who play on Steam are likely using that platform because they like a variety of different video games. Not that non-steam players don't like a variety of games, but there's a big reason I never bothered even making a Steam account. I'm not tempted by sales for games I don't intend to play.

I legitimately don't know anyone who plays FFXIV on PC and doesn't use Steam for other games. The only difference between Steam FFXIV players and SE Store FFXIV players is that the SE Store players prefer to manage their installation for MMOs with their own launchers outside of Steam.