There are a lot of tradeoffs that go into product design. When it comes to laptops, there are capabilities (display resolution, processor speed, storage space, battery life, and so on), size and weight, cost, and upgradeability. Apple seems to have gotten the impression that upgradeability is the factor that people care about the least, and I suspect that they’re right.
Just listen to your friends who are not into tech. When their notebooks are getting old and they are starting to complain how slow they become, they are always talking about buying a new notebook and never about upgrading their existing one. Apple is no longer a brand for professionals, they now are a consumer company.