Adult content on steam is marked as such very clearly.

Under Community Content Preferences, you'll see an option for Mature Content and Adult-Only Sexual Content.

You'll also be preventing from accessing mature content depending on the filters in your account settings, and in the Family Management section of steam, for Family Shared Libraries.

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rustystump 7 days ago | parent | next [-]

Next you’ll tell us that all facebook users are over the age of 16 just like marky mark promises us.

	▲	BlueTemplar 5 days ago \| parent [-]
		It's not clear to me what kind of age controls Steam has, but I suspect that they require certain forms of payment before accessing the "super adult" portion. (For instance you cannot see the "super adult" store pages at all if you are not logged in.)

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aprilthird2021 6 days ago | parent | prev [-]

So what? A kid can still go get adult content without anyone else knowing or seeing. Most parents aren't able to set the family settings on Steam or even know their kid knows what Steam is.