This didn't happen overnight. When I was in my early teens in the 90s I already had a sense, from listening to the news, that employers were out for their own self-interest first and foremost. Massive layoffs, shrinking benefits, and the concept of public companies being primarily responsible to their shareholders all send the same message: "At the end of the day, you are disposable. Loyalty will not be reciprocated."
As an employee, it would be irrational to ignore this and hope that loyalty would be rewarded.
But isn't it doomed to be a self fulfilling prophecy if you approach every new company with these beliefs?
Google is a great example of one that started out very differently, but unfortunately became much like the companies they strived to set themselves apart from. Many startups still foster that culture Google originally had.
I think the gps point is that, in the median, it's the case regardless of how you approach it.
Of course individual situations and be quite different, but you are really bucking the trend in expecting the average company to show loyalty instead of respond to financial incentives.
As an employee, it would be irrational to ignore this and hope that loyalty would be rewarded.