>Vegetables are a better source of protein and healthy fats, and they're more efficient
not necessarily, otherwise there wouldn't be carnivores/predators. And vegetables may be not very well available: https://www.youtube.com/watch?v=y4H8JHoSrSs
>Insects are just animals that inefficiently convert calories into animal protein.
somebody converting calories into animal protein saves a carnivore a need to have longer/bigger/heavier gastrointestinal tract than it otherwise has to have. Thus carnivore can have more efficient body for movement (and thinking - apes started to become humans ones they started to scavenge and eat meat about 2 million years ago, though it is not meat eating alone or primarily, the primary trigger was scavenging and later hunting activities that caused our ancestors to pick a stone and stick as a weapon )
Note: personally moving toward vegetarianism (mostly for ethical reasons), not there yet, as of now have completely dropped beef, lamb, pork and am eating more vegetables and fish.