You might prevent a car from being broken into. They might not know if you don't call them. Fires can and do occur in campus buildings. If a fire has started consider your safety and others first before trying to fight a fire. Learn the best way to exit your building in case of fire and consider alternate routes in case fire has your main exit blocked.
Most people die in fires because of smoke inhalation rather than of burns.
Smoke from fires can be extremely dark and blinding. If your guests happen to be at the wrong place at the wrong time there can be problems. The outside doors to the building are locked for one important reason and, no, it's not to cause you grief by making you carry around another key. There have been many incidents across the country where offenders of all types entered Residence Halls because doors were propped open for one reason or another.