It reminds him or her how good he or she has it.
Your boss has supervisors running around making sure you're exhausting yourself. Your boss spends thousands of dollars making sure that you suffer.
Want a day off? You mean a day free of suffering? Oooof no can do champ.
And your boss loves their job. Why wouldn't they. Big paychecks, salary, vacation time, health care. But the unspoken truth is that the best part of his job is watching you suffer.
“Keep up the good work!” Translates to keep suffering.
“We appreciate you” i appreciate that you suffer for my biannual bonus
“Teamwork makes the dream work” I'll be upstairs counting my money