Whatever else, I can guarantee you that they are not doing it on purpose in order to make it harder to repair them. They have just been prioritizing thinness.
> or if you're paying them that much to replace the entire top case assembly
The link says that "previous" MBAs had replacable batteries, and I know that 2012-2014 had it, so I don't think it was ever the case.
> For comparison, the previous-generation MacBook Air has a screwed-down battery that can be removed and replaced by Apple and its service providers without a top case replacement, in line with other non-Retina notebooks.