I mean, they can but it takes time to do that and until they do /r/pics is adhering to the letter of the law (or at least an interpretation of it) while spitting in the face of the spirit of the law.

Ah, no, swearing is allowed as long as it’s vulgarity, profanity is what requires an NSFW tag. It’s a very important distinction that the Reddit ToS accidentally makes.

So, in conclusion: Fuck -> No NSFW tag. Hell -> Yes NSFW tag.