Pro scouts look for starters to throw 3-4 "plus pitches" and relievers to throw 2-3 "plus pitches." A plus pitch is an above average pitch compared to your peers. For example, a plus fastball is 92+. A plus curveball breaks 12-6 and can be thrown for a strike in ANY count.
Not only is throwing more than 3-4 pitches totally unnecessary -- it's also a waste of time. (Can you name one MLB pitcher who throws 7 pitches? I can't.)
Better to develop a true mastery of fewer pitches. Better to say, "I throw 92 mph," rather than, "I throw 7 pitches." Scouts are looking for those dominant plus pitches.