How do you figure? Are MacBooks heavier than plastic computers? I think Aluminium is heavier, but has better strength-to-weight ratio than plastic (so can be much thinner to get same tensile strength), but its more expensive.
I stopped using my iPad as much as I used too, but its also 5 years old. My wife has bought 3 iPhones in that time frame; i agree and think the turn-over rate is the main factor in Tablet sales declining
If they stopped selling iPods today they'd make less money in a year than if they didn't. I agree the iPod is on its way out, but it still makes money, so why stop? Eventually people will all migrate to Watch/other wearables, but not right now, so why cut the iPod early?