Escort missions... They are added in most games to add variety for the sake of variety. They are usually sucktastic because the AI is horrendous, with your virtual partner making everything in his power to make everything worse. They got themselves in the line of fire, they get in your way and repeat the same lines over and over and over again.
I am hopeful that Bioshock Infinite shows up that you can have to escort someone without it being a hassle. It can help if they make us like and actually care about Elizabeth, the virtual partner. Let's see how they pull that up.