Paper tickets cost the airline something like USD7 per coupon so ETKT are much more convenient for the airline but also for the passenger aswell, you cant lose it being the main advantage, sure enough you are supposed to carry a copy of the itin with you but these can be reprinted at checkin desks or ticketing desks.
Sure if you lose your paper ticket then you will have to pay for it to be reissued, I could never understand why people complain about this as if you lost your bus ticket, concert ticket, train ticket it wont be replaced you'd have to buy a new one..... lucky you dont lose your LX ticket as it will cost you £80 for a new one!.
Also I think airlines are trying to promote it as BA for instance will charge you a fee to have a paper ticket on an ETKT route, plus then they have your email address to add to their data base for endless special offers