what is a professional? Steve Vai? He knows all his scales. Eddie Van Halen? He's mastered scales at 12. Jimmy Page? ditto. Buddy Guy? He invented one.

If you're talking about a touring musician, or a studio musician, they absolutely know their scales.

Anyone who makes more than $20k/year with their guitar knows their scales.

Other cherrypicked examples, Dave Grohl and Clapton famously had no formal training and just learned by listening to and emulating artists they liked. I suspect they make over 20k/year.

Dave Grohl knows his scales now. Yes, if you make a band and become successful you can call yourself a professional without music theory. If you go back to what I said though, I said as a degree.