Why are they 2 ways of adding contacts to a deal?

1. Contact name ( standard field - lookup )

2. Contact Roles ( related list )

The process in zoho is first create a lead then convert it to an contact, account and deal.

So instead of adding contacts in both 1. Contact name ( standard field - lookup ) 2. Contact Roles ( related list ) can I not just use the  2. Contact Roles ( related list ) to add/ associate contacts to a deal?

and incase there isn't any contact for that account I can create a contact inside 2. Contact Roles ( related list ).

Please help me out cause our users seem to be confused.

Thanks