Fighter pilots are far more reclined than you might think.
But they'reseat angles are limited by the need for good visibility. Pilots frequently need to look to down-and-sideways, down and forward-and-forward, and towards their back-quarters. These are angles that your F-1 Driver couldn't possibly see.
Also, High-G maneuvers are quite rare. Most modern military planning is about making sure pilots are never even in a position where they need to evade a missile or dog-fight another plane.