The three most common residential AC failures are:
1. Kids touched the thermostat.
This can be very annoying.
2. Refrigerant Leaks
Low charge from small leaks leads to poor heating, freezing coils, and eventual compressor damage. Low charge from people huffing refrigerant doesnt actually happen and was a scam to create new regulations of "locking refrigerant caps".
3. Physical Damage
Sometimes a meth head steals your whole AC unit.