Who is responsible for locking the bootloader? I was wondering who is in charge of the locking of bootloaders.

I recently chatted with a representative from LG-UK enquiring about the unlocking of bootloaders. I was told that I need to speak to Google about why the bootloader is locked. I suspect this information to be false but just to be sure I wanted to ask on here if anyone knows who is actually responsible for the locking of bootloaders?
The OEMs (Original Equipment Manufacturer) or Carriers like verizon, AT&amp;T, etc Lock Bootloaders, Google Devices Like Pixel come with unlockable bootloaders via Fastboot.