The 90’s? Locked bootloaders would’ve meant people woukdve simply bought different machines without a locked bootloader.

See the IBM/Phoenix BIOS war - it’s essentially the same thing. IBM didn’t want to license their BIOS to everyone, so Phoenix reverse engineered it. If I remember right, IBM was trying to lock everyone to using their OS.

Early Android (circa 2009) didn’t have locked bootloaders.

Google wanted people to experiment, which was basically free research for them. Pixel’s today are unlocked when purchased from Google.

Even my earliest Verizon phones weren’t bootloader locked - they didn’t start doing that for a few years (my last Verizon phone in 2012 wasn’t bootloader locked). And Verizon is arguably the worst vendor when it comes to bootloader locked phones.