I always thought it's more like a nappy than bubble wrap; it's always stained with the colour of the fruit, so assumed it was there to absorb moisture from bruised fruit.
Oh yeah, sometimes there's a nappy thing, but I'd say bubble wrap is more normal for strawberries. I think the nappy thing is impregnated with something that absorbs ethylene. See http://www.itsfresh.com/Absorbing_Ethylene.html
