That's partly because nesrly nobody, including Linux vendors, actually pushes or checks for parameters being passed from BootVar to executable. Just like barely anyone apparently supports BootVar hotkeys.
Nobody uses it so nobody actually bothers with it, and even Linux defsulted to storing the params in files or kernel itself because good luck finding out you can put them in BootVar at all.
It's still miles better than it was with BIOS, or even Unix workstations (including OpenFirmware ones) with their "emergency releases" of updated OS just to make it boot on new gear
Nobody uses it so nobody actually bothers with it, and even Linux defsulted to storing the params in files or kernel itself because good luck finding out you can put them in BootVar at all.
It's still miles better than it was with BIOS, or even Unix workstations (including OpenFirmware ones) with their "emergency releases" of updated OS just to make it boot on new gear