Whether it be electronics, automobiles or medical equipment, the manufacturers should not be able to horde “oem” parts, render your stuff useless if you repair it with aftermarket parts, or hide schematics of their products.
Summary video by Marques Brownlee
Great channel covering and advocating right to repair, Lewis Rossman
Basic blender went bad (motor ran but spindle wasn't rotating). I wanted to disassemble to see if it could be repaired. Three of the four screws were Phillips head. I had to cut the casing open in order to discover why I couldn't unscrew the fourth. It was a slotted spanner.
That belt clip is there to make the knife technically legal in some areas. A 3"+ blade can't be concealed by putting it in your pocket, so the workaround is to have the clip showing on the outside of your pocket, making it visible. That's why they use screws like that. At least that is my understanding - I could be wrong.