If rubber is a good insulator why do balloons attract static electricity?

Insulators can easily have static electricity. In case of conductors we have to follow some delicate procedure to store charges on it. Usually that is known to be electrostatic induction. But in case of insulators just rubbing would do to produce static electricity. Example: when a glass rod is rubbed against a silk cloth, then glass lose electrons to the silk and so glass becomes positively charged and silk negatively charged. So balloons being a bad conductor is good example to have static electricity. If it is good conductor then charges would flow through them easily and so not possible to produce static electricity just by rubbing.