I have no problem with this design choice as long as the standard capacity isn't scarce, which it isn't. I think 8GB of memory and 256GB of storage is enough for the vast majority of users. And it's not as if there is a faster storage technology right around the corner. When MacBooks shipped with HDDs and SSDs were about to become a lot cheaper, upgradability was very important. Now Apples soldered SSDs are the fastest in the market and you don't even want to upgrade to something else. I'd rather have them better integrated into the system with a custom Apple SSD controller and so on.