Ah yes. I remember feeling, mistakenly, that I was indispensable and that the company would collapse if I took leave. Truth is that I probably would have collapsed if I didn't take leave.
I guess the bottom line is that a firm is under-resourced if it can't afford to honour it's staff holiday entitlement.
Anyway, I am now retired and the firm I left is still going strong. They're not missing me at all, damn it!