Why the hell are there so many 7 trains?

I don’t use the line often, but every time I do, there’s a train coming every 1-3 minutes. And even during rush hour, the trains are less than half full—literally less than a quarter full. Because there’s always another 1-3 minutes behind that. My more often used lines are coming every 12-15 min. Can’t they repo a few trains from the 7 to spread the love? Wtf mta