Why doesnt Cato attack Katniss and Peeta Mellark?

Cato does not attack Katniss and Peeta because they are strategically advantageous to him in the arena. He is aware that they have formed an alliance and that their strength as a team could be a threat to him. Additionally, Cato is focused on eliminating the remaining tributes and winning The Hunger Games, so he chooses to bide his time and wait for the right moment to strike, rather than engaging them directly.