A lawyer will make sure everything is in order legally. They won't get the best deal for a player. A good agent will drum up interest in their client any way they can.
Clubs would try and get young lads signed to long contracts on low wages. Clubs took advantage of players for years - listen to Mark Crossley talking about Brian Clough negotiating with him. And Crossley liked Clough. Clough told him to sign a blank contract and that he had 5 mins to do it. As Crossley was outside thinking about it for the 5 minutes Clough allowed, he was getting shouts of "You have 4 minutes, son" and so on. Listen to John Giles talking about his exit from Leeds.
Where this sort of money is involved, parties will try and take advantage of each other as much as possible. Players, typically, are not as well educated as club owners. They need agents or the pendulum of power swings right back to the clubs.