UEFI is not a special mechanism to stop the installation of another OS. It's a security measure to tie the operating system to the firmware. It's also an upgrade to BIOS which was developed in 1979 and is a bit out of date. (Want to boot from a hard disk that's bigger than 2.1TB? BIOS isn't going to help you there.)
Yes, it's a real shame that Linux aficionados can't play with the UEFI hardware quite as easily as they could with BIOS, but there are work-arounds. People who replace the OS like this are truly a tiny minority. To the vast majority a PC is an appliance, and the security and speed that UEFI adds to a system is a benefit.