Why they're hardly even Scotsmen at all! Less humorously I'd say your definition of working class differs from that of the public. If you ask those tradesmen if they're working class, I'd wager upwards of 90% of them will say yes.

Working class to most people just means that they do manual labor. They work outside and in factories building and moving physical things be it burgers or buildings or balloon animals. The key seems to be that they don't generally sit at a desk with a computer on it for 8hrs a day.