They do, it's just they are not readily visible. The UL certification is for the plug and connector, not the whole cord per se. Plugs have to meet basic UL standards (UL 498) for electrical devices. The cord manufacturers do not make the plug/connector - they get them from Hubbell, Bryant, etc. The UL rating is given to the plug/connector manufacturer and not the guy that pieces the cord together. Interesting side bar: if the cord (or any other elecrtical product) is sold in stores or distributed through a dealer network, it has to meet UL/IEEE/NEC requirements for grounding, etc., but no such requirement if sold direct.
Some connectors also have what's called an "IP Suitability Rating" which rates the ability to prevent dirt and moisture (ingress protextion). An IP20 rating is common for plugs. The IP20 rating means that particles of 12.5mm or greater are effectively blocked (the "2") but no water or moisture is blocked (the "0").
Don't worry that cords will cause a fire. That's more easily accomplished by oversized circuit breakers and other audiophile wiring "improvements".
Some connectors also have what's called an "IP Suitability Rating" which rates the ability to prevent dirt and moisture (ingress protextion). An IP20 rating is common for plugs. The IP20 rating means that particles of 12.5mm or greater are effectively blocked (the "2") but no water or moisture is blocked (the "0").
Don't worry that cords will cause a fire. That's more easily accomplished by oversized circuit breakers and other audiophile wiring "improvements".