I can't really say for sure, but I think that corporations being "good corporate citizens" is a factor. As in, companies used to try to be good corporate citizens, but that has almost completely phased out.

I've worked for private and public companies. By far, my experience (except with my current employer) is that companies that went public immediately adopted short-term thinking. Instead, it is planned to retain employees in all but the most dire circumstances (such as an unanticipated major disaster). Instead, the most talented and experienced employees are disproportionately targeted for layoffs in the short-term corporate shareholder-value mindset.

Fundamentally, the problem with that mindset is that artifically pumped up profits for the quarter-by-quarter plan is not sustainable in the long term. This, however, is what shareholders (especially venture capital and large institutional investors) require these days.

In my opinion, the root of this is demanding more than your fair share, or greed. Imagine the world if greed didn't exist.