The 1 Megohm resistor is for protecting the human body, refer to question below. The purpose of the 1 Megohm resistor found in series with wrist straps, foot grounders, drag chains, and ground cords is solely to provide safety to the human body by limiting the amount of current that could be conducted through your body. Underwriters Laboratory has approved selective model foot grounders and wrist straps only with a 1 or 2 Megohm resistor in series. In general, yes. These induced charges are sources for ESD events.
Earth ground happens to be a very convenient reference voltage to connect to.
If you ensure that all conductive parts are tied to earth ground, then you meet the same requirement that they are at the same potential. The higher the RH, the less time an item will hold a charge. This range depends on your working environments. Check with the manufacturer of your devices and ESD control products for the optimum humidity range. Some ESD control products are humidity dependent such as floor finish and topical antistats.