@anthracite @CoyoteTraveller I think the appeal for me is more;
the protagonist is from the world of the normal and mundane as a relatable point of contact in a weird magical (or sci fi) world. Frequently they're an 8-12 year old boy, and as an 8-12 year old boy, I wanted to be a swashbuckling archaeologist, a musketeer, a barbarian swordsman or any number of things WAY more than an 8-12 year old boy.
By comparison the magical sidekick is ALREADY part of the AWESOME world.