Why? The majority of successful standup comedians employ people to write for them, any trace of anything creative leaves them when demand is higher than they can produce material.
There's a huge difference between people like Michael McIntyre, who is very old school, and certainly does have a team of writers, and comedians such as Stewart Lee, Richard Herring, James Acaster, Sara Pascoe, Lucy Porter, Holly Walsh etc who almost certainly write their own stuff. They tend to put their own very personal stamp on things. And a lot of those comedians are also writers - Stewart Lee, Acaster, Herring and Pascoe have all written books. As indeed have countless other comedians (David Baddiel, Robert Webb and Jo Brand spring to mind, not to mention the awful David Walliams).
I've been disappointed not to see Jo Brand come out in support of gc feminists. Robert Webb did, briefly, then deleted his tweet. Essentially, the ones who aren't stupid, by and large, are cowards.