Reagan actually campaigned on doing away with Selective Service as a waste of taxpayer money. All it does is pay armies of bureaucrats to compile a huge mailing list. If something goes down most of these people won’t be found, or if they are many will resist and clog the court system.
After getting elected he changed his mind as it was thought this would send the wrong message to the Evil Empire.
And it’s not even a good mailing list. It’s not like you’re required to update.