When you do the screw-attack or morph-ball in the Prime games, it pulls out to a third-person view.
This is a brilliant balance between views to make the gameplay in those modes more accessible. And few would argue how well they're executed.
Still... I miss Samus' super dash

When they gonna put that back in. That'd be awesome to see in first-person -- just run really fast until you smack your face into a wall. Who knows, you might just find a secret.
Of course the real reason so far is that the 3D Metroids have to have a more stricter level structure to accommodate polygon budgets.