To provide more to the "why", although end-user devices have moved away from BIOS-only boot, there are large number of systems that have no alternative to BIOS, and the hardware cannot be upgraded, only the firmware and software.

Most of the systems I have ran into were in SCADA[0], PMS[1], and BMS[2].

[0]:https://en.wikipedia.org/wiki/SCADA

[1]:https://en.wikipedia.org/wiki/Power_management_system

[2]:https://en.wikipedia.org/wiki/Building_management_system