Like @Railcar8095@lemmy.world already explained, having some strong protection of data on a device like the Steam Deck, that can easily be lost/stolen seems to be warranted.

Aside from the saved login credentials of my Steam account, there are a lot more credentials saved on it, because I love to use the desktop mode as work environment.
Having someone getting access to several accounts saved in the browser or email client would be not very great to say the least.