I use the Augmented Steam extension[0], which shows a more prominent banner if a game has DRM, anti-cheat, requires a third-party account, or other gotchas. Plus a bunch of other useful features
Tags are crowdsourced. I was tagging games with "always-online DRM" before they declared it on the store page, but only the top few tags are displayed, so there's no point.
They also editable by developers / publishers and it's by design. Any sane developer prune their tags from time to time since Steam recommendations depend on them.
So it's not exactly a reasonable place to put something like that.
