Why would a terrorist want to plant a Bluetooth device on someone else's bag when all it would accomplish is a minor delay of one flight and would result in a prison sentence after security camera review??
What do you mean by etching? Google does also it's own chip design with TPUs, data centers, and models but afaik only TSMC Intel and Samsung do the actual semiconductor fabrication
So that you don't accidentally run malware. MacOS is not iOS, you can run unsigned code if you really want to, but it will make you jump through a few hoops.