When it comes to short trips, I don't think it is a lack of gear that necessarily puts people at risk but a lack of awareness. By that I mean, constantly assessing where you are with respect to the trail head, your energy level, and the weather etc. A short trip is by definition just that, meant to be short. By ignoring your situation and wandering around as though you have all the time in the world you will run up against reality and get caught out. If your plan is to explore and not keep track of your situation, carrying a small pack with basic survival gear is a good idea.