The guys who are well known hobbyists (as opposed to industry professionals) must absolutely love chatting about pipes but I don’t think any of them are on the forum. Where do they get their fix of pipe talk if not on a forum? Some guys that come to mind are Fred Hanna and Rich Esserman or other Doctors and Masters of pipes.
First, I'd say there are plenty of well-known pipe smokers right here in front of you.
Secondly, how do you know the folks listed are jonesing for pipe talk that can only be obtained through forum participation? Or that they aren't already participating, and we don't know as they are using a clever screen name? The only way to know is to ask them directly.
On another forum, I frequent a well-known individual (in this case a performer and small business owner) was an active participant, he didn't try to obscure his identity. Eventually, he was driven away by various trolls and folks who took issue with everything he posted. Maybe that tale sheds some light on why prominent folks don't frequent forums. BTW I've never seen Tiger Woods or Jon Rahm on any of the multiple golf forums I visit.