Why are people somewhat jealous or envious?

I've been hunting GT caldonterrus for a week now and one thing I've noticed is that low tier people hate to see high tier or expensive creatures grow, I don't even attack or provoke them to do it, I always see them do the same with high value creatures and always these attacks are made by "cheap" creatures, once I was helping a guy with his galiryn mut hunt and several Kriprik searched for us for a whole hour all over the server to steal our eggs, we never did anything to them, they just didn't want us to have any Mut to sell with the galiryn