why stone cold is not wrestling these days?

Stone cold retired due to his neck injury which he had very lately with owen hart and also due to his knee problems. His last match is against "The Rock".. It was a great interesting match were Rock won the match after 3 rock bottom. Austin cited his long-time neck problems as the reason for the retirement. He noted he had several MRIs prior to Wrestlemania, but didn't discuss them because "I'm Stone Cold Steve Austin." Those problems were actually the primary reason he walked out of WWE last year. "I've got some serious problems in my neck. It's too long and too complicated to discuss. But a lot of the reasons I walked out of this company seven or eight months ago were things I didn't want to talk about at the time because we had WrestleMania coming up. The biggest reason I walked away was because my health is going downhill so badly, and I can't compete at an acceptable level to me, and at a risk factor that's high enough to me. Everything I do in that ring is very dangerous and makes me go even further downhill. It's potentially something where I could end up being a quadriplegic. That was the biggest reason I walked out. The creative and the political issues were just icing on the cake -- the straw that broke the camel's back."

He has had so many injuries to his knees and other places that he wants to be able to live some. The doctors probably told him that if he injured his knees again that they couldn't put him back together again.