..and there are plenty of non-nefarious reasons to want to spoof numbers. I used to have a VOIP setup at home that, when I dialed out, the call would appear to come from my cellphone[0]. Google Voice used to be able to do that too (no idea if it still does). Businesses often use this to have all their calls appear to come from the main office line or a 1-800 number. Or, when forwarding a call, you could make the 2nd leg outbound call appear to come from the original caller instead of the forwarder, things like that. Unfortunately as with so many things, bad actors are going to ruin it for everyone.

[0] I also found out that if I dialed my cell phone voicemail number from this VOIP phone, it bypassed my security code and went straight to my mailbox - since the outgoing number matched my cellphone number, it assumed it was me calling. A quick experiment showed I could then access anyone's voicemail (on that carrier at least) by simply setting my outbound number to appear as their cell number...