Teams carry enough pitching as it is. It wasn't to far back when 10 pitchers was the norm, 5 starters/5 relievers. That's not even going into the few years in the late 80's where teams were keeping rosters at 24. Now, the standard is 5 starters/7 relievers. If you keep 1 or 2 young pitchers in your bullpen in the 11th and 12th spots, they generally have options you can play with to manipulate the roster. Or, teams could learn to let their starters go 7 innings when they are pitching well. They won't expand rosters because that means more players accumulating service time, which means quicker to arbitration, quicker to free agency, and they are off the cheap 1st 3 years of control that much quicker. Some teams don't even call up their best prospects in September in order to avoid the accumulation of service time.
'Ric Flair wishes he was Paul Roma.' Congratulations Paul on winning the Idiotic Comment of the Decade Award.
Why not add two roster spots so teams can carry more pitching?
You really want more pitching changes?
Why do it? Do you think there's pitching unfairly being kept in the minor leagues because of roster sizes? It seems like if everything was merit based, it'd go the other way, and teams generally carry at least 1 guy who isn't major league quality but the team needs x many pitchers and doesn't have a better option.