You're overreacting to this. Who upgrades the RAM? Only techies and people who actually need extra RAM. Not that many people are going to need to upgrade the RAM over an iMac's lifespan. 8GB is plenty. I only have 6GB in my Mac Pro and don't see the need to upgrade it.
By the way, the number 1 killer of old computers is new web standards and new websites that use them (thanks Google et al.). It's the only software that updates itself. New software is almost always programmed less efficiently and requires more CPU and GPU usage. Flash has gotten even slower, HTML5 was always a pig, and all these new web elements and useless social media "integration" on websites slow any old computer to a crawl. Just to give you an idea, simple Google search lags on an iMac G5!
One of, if not THE easiest way for a non-techie to increase the lifespan of a machine is to upgrade the ram, its the LEAST techie thing you can do for the biggest performance gain on an old machine
However, if you need technical help to change the batteries in your remote (or do you just buy a new TV or cable box when they run out ?) then maybe you have a point.
As for No1 killer being web standards, WRONG, i have a PPC G4 Mac Mini going strong that my mother uses, the only issues it runs into is H.264 video encoding, everything else, HTML5 CSS etc is all runs fine, just the old CPU cant cope with realtime HD video decompression.
Google lag doesn't effect it, so i don't know why G5s were having issues, no experience with a G5, just the lowerspec G4 that doesn't have that issue.
Lets face it, if mobile phones with MUCH lower spec hardware can cope with modern web apps, any PC, be it X86 or PPC built in the last 10 years should chew through all web standards , its just processor intensive video decoding that causes problems
if you think HTML5 is something that requires processing power, man you don't know how software works.
Still, the bottom line is still the same, Apple are making systems that cannot be upgraded, to force buyers to upgrade, its a good CON, release a new OS every year that eventually makes your 3 Year old machine bog down so much you need extra Ram, but wait, you cant go spend $60 on an upgrade that will double your performance and buy you another 3 years, no, you have to come back to apple and spend $1100 again, and landfill that old one.