In the main, comedians are troubled people and a lot of them are better on stage than they are in real life. I'm too young to remember the heyday of, say, Mort Sahl, who is still alive and performing periodically, or Tom Lehrer, who left the business to return to academia. We do live in an era where you can see their performances easily. Here's Lehrer with a poisoned valentine to Wernher von Braun:
And here's Sid Caesar, in a classic bit from Your Show of Shows:
And Steve Allen, with some random silliness:
These days, we clap at comedians more than we laugh at them. I'm not sure it's progress.