Well, color me surprised, I always figured the usual definition of 'professional' means he or she who is schooled in their art and using that knowledge professionally, not 'those who don't get their hands dirty'.

I find it hard to see a machinist not as a professional but fine, I'll change my internal dictionary.

Reading https://en.wikipedia.org/wiki/Professional it looks as if this is a cultural difference.

Edit: thinking about this a bit longer, it seems clear that the distinction was made by those who don't get their hands dirty at the expense of those who do, and it seems extremely demeaning to me. As if the 'white/blue collar worker' distinction wasn't bad enough now people who spend a lifetime acquiring the knowledge to do their jobs are not even allowed to be called - or call themselves - professionals.