In my opinion, it's * part bad engineering (I find their concept of loadable modules and a central dispatch mechanism that can override pretty much everything

In my opinion, it's * part bad engineering (I find their concept of loadable modules and a central dispatch mechanism that can override pretty much everything absolutely misplaced in the context of firmware), * part politics (the rumour mills claims one of the reasons UEFI was done in the first place instead of going for Open Firmware, which was an established standard back then, was to protect Intel's BIOS partners from having to compete in an existing ecosystem that was quite alive and dominated by others. also NIH), * part growing scope (Secure Boot locks down said dispatch mechanism through signatures when its inherent insecurity became an issue), * part cluelessness (Intel is good with silicon and processes, but generally not so good when it comes to software, and they shaped EFI and through that UEFI). I don't think there's malice involved, and the competitive angle is covered in politics. That it's pushed the way it is has lots of complex reasons. One is certainly pride (even if they wanted to, Intel can't simply back down after promoting that stuff for 15 years without losing face). It also doesn't help that the only realistic existing alternative for an OS-facing API remains BIOS (because OpenFirmware never really existed on x86 outside laptop.org), which has its own set of issues (even if they are all patchable with enough effort).