By its very difinition , an e-ticket combines the issuing and delivery of an airline ticket into a single operation and eliminates the need for a physical ticket. It benefits the customer and the travel agents, as a quicker and convenient way of buying tickets. Also ask the tickets would less , as there will be no printing , processing and distribution costs involved.
IATA permits travel agents to sell air transportation without issuing printed tickets and passengers to check-in and board flights without holding printed tickets, which is how e-ticketing was conceptualized.