I'm not an expert, but I've often wondered why cats like treats so much, and I did a little searching. I think the main reason is an ingredient called animal digest, which would be represented in the ingredients list under natural flavours.
I believe animal digest is to meat what simple sugar is to complex carbohydrates. Humans really like sweet things, probably because evolutionarily it helped us eat fruits and vegetables, which are rich in vitamins and nutrients. Present day, food manufacturers can exploit this through things like corn syrup. Cats can't taste sweet, as far as I know. But like humans like sweet things, cats are really into the umami flavour. It sounds like animal digest is very high in umami flavour and scent, which for evolutionary reasons (finding energy dense foods) is really attractive to them.