Is agency approval requred for all equipt

Just wondering as I have seen/owned many items which are not stamped w/ agency approvals (UL / CE etc.). This includes electronics (amps / preamps / digital) and cables (power in particular). Seems like some of the "boutique" companies do not always have agency markings. And if the equipment is not agency reveiwed / approved, is this risky for the consumer. I also wonder what liability (if any) the manufacturer holds if a fire or problem would occur. Just wondering...