A lot of that is things like the money you pay a babysitter or kid washing cars. It's not worth the effort to actually tax it.

Then some rules are unfair: for example in my business the more hours I bill the more money the business makes. I can bill more hours if I hire a cook, painter or child carer. Only I'm not allowed to. I can understand why - this could be abused - but also allowing it might actually boost the economy. Those helpers would be earning money which would also be taxed. A lot of people have their parents around who do that unpaid which is the reason it isn't allowed.