E-tickets are a huge advantage. A lost paper ticket in a remote corner of the world is a disaster. A lost copy of an e-ticket receipt is only a problem until you can get to the nearest internet computer and printer. E-tickets still require a paper copy of the receipt (=PITA), but this sure beats the old red carbon booklets.
My brain always equated that bundle of tickets (e.g. RTW, perhaps less so for one-sies) to a Valuable Thing so I always knew where It was and wasn't about to lose it.
True enough the airline thought it was valuable too and might have charged me for a replacement, perhaps at today's point-to-point price. But as expected that never happened.
My brain thinks anything associated with an e-ticket is computer-generated paper, worth a fraction of a penny. It's included in our packet of hotel and car reservations and treated with the same (lack of) importance. None of it is essential - I "know" if need be I can always show up at the counter, state my name and desire, and all will be well.
And if it's NOT all well, nothing on any e-paper will make it better. "That's not what our records show."
That paper coupon had some authority - if I showed up for my flight, no matter what, I was owed something for it. If the airline had gone out of business overnight, I might be severely inconvenienced, but at least I had something instantly recognizable by everyone in the business that probably would have gotten me on my way.