I have seen couple videos, one was a drone killing Russian soldiers, other ones were for porn. So it may just be lack of interest, or lack of convenience to share videos.
What I would do is upload videos to peertube instance (the peertube servers are better equipped for storing videos and most of them are free + offer more or less unlimited storage) and for pictures use plethora or pixelfied. Lemmy and mastodon are just one aspect of the whole fediverse, there's all sorts of instanced equipped to be all sorts of things
https://fediverse.info/
You can go to/c/kidsbeingderps to see some gifs in action. It’s a new community so there’s not much, but hope it grows. Using Memmy app, I can see the gifs in action as I scroll, similar to Apollo.
I've always hated reddit hosted videos, the performance was terrible. A link to youtube was always so much faster. I guess it made sense for subreddits that focused on video content, but I never cared about any of those.
This is why I prefer kbin over Lemmy. -- I'm posting this on kbin.social right now.
Kbin honestly looks like a drop replacement for Reddit. If you were not paying attention and had given Kbin the Reddit logo, you could easily mistake this for Reddit. Plus it is further developed along.