Why did Charlie leave the show?

"Are you under a rock?" Really? Is it necessary to be nasty? This question is the most reasonable of all questions regarding this show and simply because someone doesn't read TMZ or Page Six doesn't make him clueless.
Our whole culture has gotten mean. Once it was common to point to the powerful and kick their butt but now with the anonymity of social media we treat each other like this. Snark is too much of the norm, it's way too easy: it's the idiot's version of winning. We're constantly trying to draw attention to ourselves and I think that we want to think of ourselves as better than that.
I believe we are.
You don't need a suit of armor; you can act like a knight without being on a horse. We can all just be a little better than we are. I would just love to see a Renaissance of decency.
Charlie Sheen was a victim of mental illness. He paid the consequences for his behavior while he was sick. It was tragic for many: Chuck Lorre. Lee Aronson. Sheen. Jon Cryer, mostly Angus Jones who was strongly affected by the whole thing.
What's sad is that it became entertainment for a lot of people; human devestation as mass entertainment. Sheen worked hard to become well again and his subsequent series, "Anger Management" was VERY good.
It's no different than Jack Soo leaving "Barney Miller" because of Cancer. Christopher Reeve cancelled a two picture deal for a Spinal injury. Selma Diamond on "Night Court." Patty Duke was post pilot with CBS in 1982 when hit with bipolar syndrome. Paul Newman died before "Empire Falls" was completed. Jonathan Larson died after the final dress for "Rent." Kelsey Grammer took two years off when his sister was raped and murdered. These people are people.
Imagine if we treated Sheen the way we'd treate a friend or colleague. And by the way, Sheen apologized to Lorre and Aronson as well as the 250 member company of "Two And A Half Men" after he became stable and more healthy.

John Cryer, a remarkably gifted character actor, has appeared in his tightie-whities many times. As a young man it wasn't as noticable but as seasons pass it's very clear that he has a surgical scar on his abdomen, left side a few inches above the belly button which rules out both appendix and hernia. Any clues?