As far as I can tell, most people are not free to install AOSP on hardware they have paid for since the bootloader is locked.
Even those who purchase hardware where the bootloader can be unlocked, it takes much deeper technical knowledge to install a third party OS than, say, a third party OS on a PC. And that is assuming someone else built the OS for you.
Even those who purchase hardware where the bootloader can be unlocked, it takes much deeper technical knowledge to install a third party OS than, say, a third party OS on a PC. And that is assuming someone else built the OS for you.