Your Trainer's level affects quite a few features in the game. The higher your Trainer level, the stronger and rarer the Pokemon you will encounter and the higher you can increase your Pokemon's CP.

Does CP increase with trainer level?

The higher the level a Trainer is, the higher the CP of a Pokémon can be. ... Wild Pokémon caught will also have higher CP as the Trainer levels up.

Does trainer level affect IV?

This is a confirmed, systemic change to how IV's, moveset, height and weight are encountered, travelers.