People have rose-tinted glasses for BIOS, have no idea of all sorts of hidden complexity that was involved in it, assumptions, etc. Or all the broken ideas that vendors put into BIOS-era firmware [0].
People also rarely think of the complexity inherent in having an open platform where owner of a device does not need to build/acquire a custom OS build for their machine, and thus see cases of "enough to run something they care about" and think that's enough.
[0] I still remember BIOS config menus and PCI card option roms that effectively had stripped down windows 3.0 in them, or an approximation of it. And how it meant presence of Intel PCI hardware RAID controller in certain server meant I needed a full crash cart or remote KVM to fix RAID config.
