Do you know why Reddit actually built their own multimedia platforms via i/v.reddit? Because Imgur didn't want to host Reddit content anymore [0]. This is about NSFW but more generally there was a cooling of relations between Imgur and Reddit because essentially Reddit users were freeloading on Imgur's platform without Imgur necessarily being able to show ads due to how Reddit linked directly to the image and not the Imgur link. Therefore, Reddit was forced (and yes, also wanted) to build their own versions.
There is no free lunch. Someone has to pay the bills on hosting, and I'm sure Reddit thought it'd be cheaper to do it themselves at scale than to pay someone as a middleman.
This is the Reddit announcement about their hosting [0]. At that point in time, Imgur was already redirecting direct image links to the non-direct wrapper page so that they could show banner ads. This made it difficult for Reddit to show images in the site and app well, thus the cooling of relations between both I had mentioned. It's interesting since Imgur started off as "an image hosting service that doesn't suck" according to the creator, on Reddit [1].
imgur started as site to host and hotlink images published at reddit (they wanted to change it to be profitable, but entire point of Imgur was to enable "freeloading on Imgur's platform")
There is no free lunch. Someone has to pay the bills on hosting, and I'm sure Reddit thought it'd be cheaper to do it themselves at scale than to pay someone as a middleman.
[0] https://www.theverge.com/2019/10/18/20920977/imgur-reddit-ns...