It is my understanding that the virus is spread through respiratory droplets (so coughing, sneezing, spitting, etc.), being breathed in, swallowed, entering the bloodstream, going into the eyes.
In that sense, I'm not sure wearing gloves (even for as short a time as going out to the market) really helps: You'd be touching door-knobs, shaking hands, patting(?), then touching your face and eyes and breathing in those droplets (or other people would be then touching their faces and breathing in YOUR droplets). Whether or not you wear gloves won't change this.
If everyone was wearing gloves, goggles and a face-mask when they go out, then when they come back in, throw away their gloves/mask and wash their goggles, it would make more sense.
If I'm wrong in this understanding, feel free to correct me.
EDIT: I suppose handing out disposable gloves at the supermarket would help in situations where you might be infected/have come into contact with the virus somewhere on your hands, you wear the gloves, do all your shopping, DON'T touch your eyes or cough into your gloves/wipe droplets with them/sneeze into them, interact with someone else who might have the virus, and then throw them away once done. So they're not useless, but I feel a better system should probably be put into place.