[mabster]

Companies have complex telecoms but generally want the outside as one company number. Solution, the sender send a packet with the number they should get perceived as. Everyone sends this on. Everyone "looks the other way" by design haha

[mschuster91]

So what, gate that feature behind a check that you can only set an outgoing caller ID belonging to a number range that you own.

The technology to build trustable caller ID has existed for a long time, the problem is no one wants to be the one forcing telcos all over the world to upgrade their sometimes many decades old systems.