1. It's unoriginal.
2. If you get to the 250 top users just by reposting images that would be unfair for the other people.
3. Arguments, a LOT of arguments.
4. It's kind of like copying test answers, unfair.
5. Memes are memes but if a meme is VERY popular that meme might be reposted to the point where its just annoying or literally everywhere.
and the list goes on.