The Majority of all users won't touch the inside, but if you think a large # of users wouldn't like to add their own RAM
You were originally talking about hard drive replacement ("If Apple made it thicker slightly for better cooling and possibly easier to replace hard drives on your own most everyone would love that.") Now you're talking about RAM, which anyone can do at any time with any Mac, easily.
That's called moving the goalposts. Did you think no one would notice?