A couple of points. Surely all people who are 'entertainers on TV should be taxed the same? From reading about this, it appears to be not the case.
Secondly, years ago all TV/radio people were employees of BBC or ITV. Then all these companies sprang up making programmes, and subsequently the regulars made themselves companies, and their salaries were paid to the companies. They then took a regular wage from their company.
I paid PAYE all my working life, so I don't pretend to understand tax law then or now. But I do know that I paid my tax, not a penny more or less. I avoided paying unnecessary income tax; in years gone by I claimed for mortgage and children etc. People who pay more tax than they need are daft.
Final point is that we can all remember TV People who were on our screens all the time. And then suddenly, they weren't, and we never saw them again until, as Z listers, they appeared on a reality show. I think these companies are a hedge against that.