I suspect a comment above you spelled it out: corporations value stock price too highly.

When stock price is all that matters, cutting costs wherever they think they can get away with it is the end result (over a long enough period, I'd assume this will always happen as execs cycle through)

As things (engineering, components, design, UX, etc) are cut, customers notice - and switch to brands that they percieve as having cut less. One example of this I'd assume is Apple.