And yet that exact kind of data is all over reddit in ways that are impractical to enforce by case by case DMCA. How many memes are there using footage from popular shows? How much fanart?
More importantly, is that stuff not included as part of the data that reddit "owns" when they sell their data to tech companies? Because whether a DMCA takedown has been requested on that kind of data or not, doesn't change the fact that they don't hold the copyright in the first place. How can they sell things that they don't even own?
Something smells. The logic of this entire industry doesn't add up.
I think you're conflating two very different things here.
The DMCA covers hosting and dissemination. If a user submits copyrighted data to Reddit that they do not own and Reddit unknowingly (because, to be fair, they can't know what is or isn't owned or by who), then Reddit is not liable for copyright infringement as long as they comply with DMCA takedown requests from people who claim to own the original IP.
But again, none of that implies that Reddit themselves (or Twitter, Facebook, TikTok, etc.) can realistically claim ownership over all of the data that is on their website. The reason they are subject to DMCA at all is because there is a globally shared assumption that data that users submit may or may not be owned by some other party, and while the DMCA protects them from being held liable for simply hosting and disseminating that data, it does not magically make them the owner of all data that hasn't had a DMCA claim made against it.
In other words, if I post a picture of Homer Simpson on Reddit (and there are many), it is ridiculous for anyone to suggest that they have any intellectual property rights over that picture, that character, any trademarks, etc., whether someone has made a formal DMCA take down request or not. And if they don't own the picture, the character, the trademark, etc., when what exactly are they selling (licensing) and where did they get the right to sell it?
They might not be liable for just hosting/distributing it, but just like you can't sell someone else's car, you can't license out someone else's IP.