As someone else pointed out, it's not about the scammers. The scammers could however be hampered if the phone system was safer.

There's no reason why the phone system should allow my number to be spoofed, but that's what happens. There might be some companies that benefit from having all outgoing calls shows coming from some main number, but in that case a solution where a set of numbers are allowed to pretend so be some other number could be implemented. The majority of scams I've encountered and have heard about involves someone calling you from a random number, belonging to someone that's not involved, but who are just having their number misused. I assume this is to avoid getting blocked or looking legitimate if the target looks up the number.