You mean by how VAT is not paid on materials a company is going to use (at least that's the case here in France, no idea what the rest of the UE does it). Or by doing undeclared work?
Just had it happen to a friend: needed a plumber, impossible to find anything reliable (no one in town knows of a reliable plumber; it's a rare find). All Google Maps results contained lots of paid 5-star reviews (ratings with a full, typo-less phrase, praising the company in very generic terms, and the only review for that profile), so he had to pick one of them anyway.
Guy shows up, doesn't present a quote before doing the work (mandatory for >150€), does a mess but fixes the issue in less than 30 minutes, bills 200€, or 250€ if you want a receipt. No paperwork whatsoever, and in a position to physically harm you or do damage to your home if you refuse. And that's a "good" one. Locksmiths that charge 500€ or more for 10-minute jobs are a dozen a legion.
Then, these same people start buying cheap houses here and there, and in 20 years they'll be worth so much money that they'll become rich landlords and live on rent alone.
Several friends during PhD were renting cheap apartments whose owners were truck drivers, electricians, etc.
The point is, concentration of wealth and never-ending property values going up is only going to make becoming renter a better and better deal. And every profession that caters to renters is going to get some share of that money.
> No paperwork whatsoever
> in a position to physically harm you or do damage to your home if you refuse
So it's not "blue vs white collar jobs"; it's being a law abiding citizen or not.
I know a lot of people who matches what you're talking about, but they all have in common to have their own interpretation of the law. There's not a single thing they do by the books.
They're just "blue collar crooks".
Of course they can "win" if they cheat.
Recently I even needed my rims redone on my car, went to a big autoshop in my town, the owner came out with me to look at the car and went "mate it's going to be £500, cash only, you know how it is with the taxes. Or I can give you an invoice but it's going to be £600".
I literally turned around and left. Yes, they are crooks and fraudsters - but in my experience it's completely normalized. If you can get away with it, they will do it, and since everyone seems to be getting away with it, they do exactly that.