Blimey I'm surprised you want to travel on something as "old" as an A380. I would have thought you wouldn't settle for anything with more than 500 airframe hours. There is a problem with your way of thinking. If you don't keep anything in useful, money making service for its intended lifespan you increase the costs of that asset. And that cost has to go on your ticket. So if they had scrapped the "tired knackered old 747" before now for newer aircraft they would have to increase your plane ticket to pay for the fact they did not get the design life out of the airframe. Its the same for all assets be it aircraft, trains, buses etc etc. The only reason the 747 is being scrapped and taken out of production is because of the ETOPS rating that the likes of the 787 and A350 can achieve.
They have gotten the desired life out of the airframe though. The 747 lasted a lot longer than some of it's rivals such as the L1011 or some of the McD range. Same with the mk3's, they've lived a long life and now it's time for the razor blade factory.
Sure new models that are far more efficient save money and make sense economically but passengers also expect a certain level of service, and no matter how many times you refurb a 747 or an mk3 it's still clearly the same old dated junk underneath. I know I'm not the only person who avoids airlines flying 747-400's on longhaul routes, and I suspect there's quite a few who avoid the railway due to the mk3's.
In western European countries the trains rarely make it as long as ours do before scrapping, most of the NS stock in the Netherlands dates from the 1990's or later as they realise you can only refurb up to a certain point (ok the DDM1's are 1980 but they're going very soon and were only brought back to to shortage of decent stock).