The 24 hour wait period is so the scammer can't use the element of urgency to keep the victim on the phone where they don't have the opportunity to speak with trusted friends/family who would stop the scam.
See also https://en.wikipedia.org/wiki/Cooling-off_period_(consumer_r.... It's an old solution to an old problem: give the potential victim a chance to think clearly while the damage can still be undone.
See also https://en.wikipedia.org/wiki/Cooling-off_period_(consumer_r.... It's an old solution to an old problem: give the potential victim a chance to think clearly while the damage can still be undone.