. . . why aren't the all-time pitching records being broken?
Why hasn't someone struck out 500 in a season?
Why hasn't someone won 50 games in a season?
Why hasn't there been 25 perfect games per season?
Because the pitchers don't pitch nearly as much as back in the day. Christy Mathewson started 56 games in 1908. The most Johan Santana has ever started is 34. Almost 400 innings for Mathewson in a season and Santana only gets 230 or so. Will White pitched 680 innings in 1879. Just doesn't happen in modern day baseball as the athletics have improved so much that an arm can't hold up that many innings throwing that hard.
Pitchers will always get hurt because the human body isn't designed to throw a baseball .... steroids can't prevent rotator cuff tears, elbow ligament damage, etc ... in fact, roids probably causes more injuries in the long run.
In addition to the fact that, as stated above, pitchers today aren't conditioned/trained to throw more than 120 pitches, 225 innings per year anymore. Add on: juiced balls, tight strike zones, band box parks .... steroids can't overcome all these obstacles to winning 30 games.