Nope it's to avoid injury which other somebodies say is not a falsehood.
- Canada Cup
SI writer Tom Verducci wrote an article a few years ago declaring that a young pitcher should never increase the most innings he's thrown in a season more than 30%. He wrote it in a way that made it seem like it was backed up by data.
It's subsequently been discovered that there's no data that backs it up. The data shows more and more young starters have been getting throwing related injuries in the past few years. The data also shows that more and more young pitchers are having their innings limited for the purpose of preventing arm injuries. 2+2 = limiting innings isn't reducing the chance of injury.
Another hypothesis is that these blue chip pitchers are getting injured more and more because they're throwing more and more breaking balls at younger ages that puts unnatural stress on the arm and by the time they reach their early 20s the ligaments are giving out.