It's not even only Apple anymore. As far as I have seen, the Microsoft Surface Pro suffers from the exact same limitation. Practically every manufacturer who wants to build some high-end, but still thin and lightweight laptop runs into this problem.
What's the deal with the dell xps 15 and precision 5520 laptops then? They're 15 inch but they're still pretty thin and light (1.78kg for the precision 5520), but you can get them with 32 GB of RAM and their battery life apparently isn't terrible. I'm planning on getting one and never realised this was a compromise.
