usually

No, quite the contrary.

Facebook, TikTok, Instagram, Twitter... have paid moderators. That's a small number of massive social media sites. Forums, including their descendants in the form of reddit and Lemmy, and IRC chatrooms with their descendants in Discord and Telegram channels, are primarily user-moderated (with paid admins intervening in more complex situations when needed). Even Facebook offers groups that function like this. Number-wise the latter sites are way more numerous (but with a smaller userbase), and historically older (if it's not too pretentious to speak of the history of the internet). They are the default. So my point is that reddit didn't offload the work, because nobody (especially in the early years) thought that it was reddit's work in the first place, it's just providing a large playground and you do the rest.

The traumatising part of moderation is dealing with child porn and similar, which is not much of an issue on traditional forums and chatrooms, and tbh I don't think it is on reddit either. The worst the traditional mods deal with is harassment if they come across some aggressive loony.

Idk, I used to moderate two (rather tame) subforums, it was kind of like picking up trash from the ground and throwing it in the bin – not super pleasant by itself, but satisfaction came from knowing that the place is a bit better off than before.