Reposting popular material isn't a reddit thing, it's a human thing.
There will always be someone who just discovered that whatever from a couple years ago and likes it enough to post it. The larger the user base, the more common this becomes.
Voat (something I used before I realized it was just a racism thing (I know, I know, it's very obvious in retrospect)) would point you at an existing post if you posted the same link.
The execution was bad, and I have some issues with the concept, but it did make me think maybe there is a solution to that particular problem.
In a different universe, most social medias use OCR and image recognition technology to handle this instantly and easily. This meant a huge reduction in bandwidth and storage issues on the great WWW which eventually lead to world peace.
This universe seems to be... Behind where it's supposed to be?