I'll assume you don't understand the purpose of 'roiding. It's a recovery boost. PItchers did it because throwing a baseball breaks down the muscle. They'd be healthier for their next appearance. Hitters did it to be stronger. They could upgrade their workouts to remain strong, or get stronger, during the season. Being stronger is obviously good when striking a baseball. 'roids didn't make pitchers better pitchers. It just made them the same pitcher more frequently. No pitchers bulked up like Bonds/McGwire.
Of course, in the case of Clemens, he'd work his legs hard in the off-season and be a better pitcher for it.