Well of course predators had to evolve/adapt like all species.
On the other hand the reason they are 'holding back' is because that is what they're brought up to do. They have to go through initiations and solo hunts, but it really is more of them doing it for the thrill of the hunt, they could easily kill people like that but they choose to use all of their abilities to make them the stealthy hunter we know them as.