You're conflating "beneficial to an individual" and "reproduce more." Reproducing and successfully raising young requires time and energy that an individual could use towards personal survival.
Evolution is a game of balance. On the face of it, a predator being faster and stronger so that it can catch more prey seems like an obvious benefit that would catch on. But the time, energy and resources to do that might draw from what's needed to reproduce and raise young.
Evolution is a game of balance. On the face of it, a predator being faster and stronger so that it can catch more prey seems like an obvious benefit that would catch on. But the time, energy and resources to do that might draw from what's needed to reproduce and raise young.