If we make a regulation that requires protocols to change so that the caller ID to be unspoofable, we might as well also require to make it impossible to spoof an IP address or a sender email address...
SPF, implemented by most major email providers, helps to prevent FROM: spoofing.
Hell, I'm pretty sure our VoIP product drops external calls where the Caller ID matches one of its' own numbers.
These are problems we are solving. These are problems we should be solving in telephony too.