Some probably are, but not all. Many young pro footballers are as thick as two short planks and need someone with a good business head to guide them through the business of their own personal financial well being. And even the more intelligent ones probably couldn't navigate themselves through the complexities of a modern day contract.
FFS for all the money they earn there's a hell of a lot of them who have managed to become bankrupt. And I would imagine that takes a lot of fucking doing.