I wouldn't generalize so broadly. Apple certainly has some percentage of wealthier employees, not everyone buys, urban living is rising in popularity after 50 years of suburbs, etc. Economics and market desires have this funny quality of not being static.
I'll say again that we're speculating on the future here (average commercial building has a lifespan of ~40 years), not today.
The "walk to work" thing is an easy example of how the campus doesn't really interface with the surrounding environment, but it's far from the only issue.
Think about how inconvenient it is if you want to go off campus for lunch.
That's just plain false. Small-medium sized towns, research/tech parks, landfill/brownfield reclamation projects... people are realizing that it's easier and cheaper to set up a framework for things to grow organically than it is to deal with the expensive infrastructure issues that arise from how things were done 40-50 years ago.