People who buy a ticket are not necassarily given a special status or rank...
Of course they are. They are accorded the status of "ticketed passenger."
once you sign a contract it is not a privilege but both parties have an obligation to fulfill the contract...
A party to a contract only has an obligation to fulfill their duties under the contract as long as the OTHER party agrees to abide by the terms and conditions of that contract. If you don't agree to the terms of purchasing a plane ticket ("Conditions of Carriage") then the airline does not have to honor it. The two (privilege and contract) are not mutually exclusive, and in fact have nothing to do with each other.