One thing about pitching, with practice you can have close to perfect technique on every throw. Also, home plate is in the same location and at the same distance throughout the game, pitchers don’t have to hit the catcher in stride or adjust their throw to fit the baseball between defenders.
Besides that, nobody is rushing the mound to take a pitcher’s head off during his windup, and a pitcher doesn’t have to reset his feet or scramble to make off schedule throws in the face of pressure or good coverage.
QB technique can be trained to maximize an individual’s zip and distance for on schedule throws, but more natural arm talent is needed when the play breaks down. Knowing where, when, and how to throw (speed/angle) are probably all more important than arm strength, assuming a QB has the minimum talent needed to throw at the NFL level. More arm talent never hurts, but it needs to be paired with good instincts and football intelligence. That’s why Richardson isn’t projected to go #1 overall, the most important tools he needs are underdeveloped.