Why do they send an officer for hang-ups and open lines?
Because sometimes it’s an emergency and someone is unable to speak to dispatch for one reason or another:
NEVADA: Woman kidnapped along with 3 kids at knifepoint alerted police with open-line 911 call from moving vehicle (October 2022)
Swatting in Minnesota:
Swatting Calls Impact 15 MN Schools (Sept. 2022)