Adviser vs. Agent: What's The Difference?

The seemingly arcane rules of the MLB Draft state that an amateur player - someone who is eligible for the draft and has completed no more than his junior year of college - can retain the services of an adviser, but not an agent.  But, what's the difference?

Strictly speaking, the NCAA defines an adviser as someone who consults with a family while they negotiate with a team, but does not interact with the team directly.  An agent, however, is defined as "someone who tries to market a player's skills to an MLB club or communicate directly with a team on a player's behalf."  If an adviser/agent violates this description, the NCAA can strip a player of his amateur status and ability to play collegiate baseball.

This doesn't seem too complicated or unfair until you consider the other endeavors in life where someone is afforded the right to direct legal representation: any criminal proceeding, purchasing a home, negotiating a contract and a number of other endeavors when a lawyer's services are retained for a fee and the representation often handles everything directly.  By hiring someone to do this for a player, what part of their amateur status is violated?

Some further the point by noting that teams prefer to deal with agents directly, the ones who have a large understanding of amateur contracts, what goes in to them and what is expected and fair.  Furthering that point, how can the parents of a baseball prodigy be expected to negotiate the best contract possible with a professional baseball team that has comparatively unlimited resources and loads of experience?  Would Stephen Strasburg have been able to sign a record contract without Scott Boras's services?