50 games is a lot different then lifetime.
The lifetime does happen though if they're stupid enough to get caught doing it again and again :lol:
You've got guys doing all kinds of stuff to get into the bigs. They'll cork their bats, they'll falsify their identity, they'll spit all over the baseball (Gaylord Perry!) and they'll put things in their bodies that they probably shouldn't (greenies, roids, etc). You can't stop them all even if the first offense is a lifetime ban.
As an aside, in most cases, everyone deserves a second chance. The 50-game with the possibility of playing again is their second chance. If they **** that up, then they really are stupid.