The real lesson for employees is to ignore the cash value of the perks when evaluating offers. Perks can be taken away, but cutting salaries is much more controversial.
Which is why some sectors treat money as a perk (bonuses). But as much as companies make sure employees understand what a "bonus" is, there's a sense of entitlement and people quit when this years bonus wasn't as big as last years.
Companies try to do the same playing-both-sides there, too, though, which is what causes some of the confusion and ire. On the one hand, it's formally just a perk that isn't guaranteed. But on the other hand, they'll often make claims about what kinds of bonuses you can expect to get -- "baseline 10% is usual" or "we've never given less than a 5% average bonus in the last decade" -- because they want potential employees to consider it as quasi-salary when evaluating the offer.