Curious reaction
It is intended to ensure that two people working side by side in a similar role for the same employer pay the same employment taxes.
When Amazon and Google use perfectly legal tax loopholes to pay less tax, there is a general outcry "not fair, make the bastards pay more", yet when self-employed contractors do the same thing, and the treasury tries to pass legislation to level the playing field, the outcry is "not fair, I'm going to emigrate".
Why the difference? Because making "them" pay more is OK, but making "us" pay more is not?