Same goes for kernel, libc, all other libraries, and pretty much anything else. This is not an argument for not upgrading them though.
Also, sadly, almost all firmware updates fix a "problem [that] points to a specific piece of hardware" that you use.
If you have a budget to responsibly keep all that stuff up to date in your project and test to make sure you haven't broken anything, more power to you. It's a total waste most of the time, but why not? Especially if you're a consultant and getting paid by the hour
Firmware is different. It's not always possible to back out a change and you risk bricking hardware every time you apply an update, especially in the realm of PC-based servers. If something like a NIC or motherboard is performing as expected, updating the firmware for no reason is generally a stupid thing to do.
Edit: oh, you're the author. Please stop telling people to do this, or at least explain the risk. At a minimum, if the vendor provides a defect list with each update, it's not necessary to blindly apply updates. Take the changes if they're needed. It's possible you're accustomed to working on high-grade hardware that exhibits fewer of these firmware related blowups, but that doesn't mean it does not happen to people...