There seems to be the false assumption that if clubs didn't pay agents and footballers did that it would save the club money - all it would mean is that signing fees would increase.
One big reason is the way in which HMRC treat footballers.
Actors pay their own agents but those payments are allowable as a business expense - i.e. payment is made out of income before tax. HMRC don't allow footballers to claim payments made to agents as an allowable expense so most contracts...