Why would your diet be more balanced if you eat more fruit and vegetable?

Meat is mostly protein and various fat that the body need.

one should not base ones daily nutrition on proteines and fat alone.

Adding fruit and veg. gives the body more sugar, fibers, vitamins etc. in addition.

Proteins and fat are "hard" to digest and the body will tell you to relax whilst digesting it.

having some sugar from fruit gives you energy whilst digesting.

Fibers from vegetables make the stomach work better and the vegetables are rich in nutritions one would otherwise not get.

This is why it is a good idea to "balance" a bit.

Regards.