I've just worked on a system with a BIOS that tried to get smart, and IMO got it horribly wrong.
This was a working PC that came in for a RAM upgrade, so I set boot order to not boot the HD at all (I want to avoid any chance that bad RAM might have to eat the installation) and booted a 1.44M MemTest86, which promptly rebooted. So I tried my CDR, which uses a different version, and that showed RAM errors. And so on, etc.
At some point, a boot POST phase had BIOS prompt me to enter Setup, as it had noticed several failed boot attempts, concluded all was not well, and thus had (irreversably) flushed all CMOS settings back to defaults.
What's wrong with that picture? Firstly, the notion that factory-set defaults are safe, when in fact they could be incompatible with bootability. Secondly, BIOS duhfaults are often self-serving or controversial, such as disabling S.M.A.R.T. monitoring of hard drives. Thirdly, this re-defaulted hard drive bootability, which is often a bad idea in such circumstances (and the reason why I had specifically prevented this). Fourthly, the change is irreversible and permanent, whereas the cause could have been unrelated and transient (such as my corrupted 1.44M diskette).
There's more, such as malware that could boot-fatigue its way to weaker BIOS-level defences such as blocked flash BIOS updates. I'm sure you can think of others, too.
Bad BIOS, no biscuit :-)