Companies pay taxes on labour - usually as a function of 'social security' and other things - a 'human' will engender social costs down the road into which taxes must be paid.
In Canada - the only payroll tax is basically that - social security. Somewhat similarly in the US.
On the continent - it's a little more.
The reason that the government taxes labour (before income tax) is because:
A) They can. And what gov. official doesn't want to get more tax revenue?
B) It's an easy tay to hide huge income taxes.
If the EU simply transferred all payroll taxes and simply rolled them into income taxes (which would be economically equivalent) - then income tax in most EU countries would be quite massive. Well over 60% in many cases. That doesn't 'seem' very competitive, does it. Also - when you get your paycheque today in France it has x% deducted - if there wasn't payroll tax then it would be much more deducted - and the 'emotinality' of it all would be much greater. Payroll taxes are a way to 'hide' high tax rates from the commoner.
It would be more transparent if EU countries just did away with payroll taxes and put it as part of income tax - then we'd have a better picture of what is going on.
We collectivize the means of production and run the robots ourselves.