It gives certainty in tax legislation which is essential for a properly formed tax system. At the moment there is noe certainty at all.
The Labour govenment brought in what was then known as IR35, the intermeadiaries legislation.
This legislation has proved bad for business as it does not give certainty over a person's or company's tax position. The legislation has not raised anywhere as much as the previous govenment thought and with the number of appeals and cour cases it is actually costing country money.
See Jones v Garnett (The Artic Systems case).
Whilst ther is an argument for this type of legislation to stop the Friday to Monday change of employment from employee to limited company the law is so badly worded that it has caused nothing but greif to a great deal of small businesses.