There are certain nouns that are always plural—the explanation for this is difficult to find, but usually it has to do with pieces of clothing, tools, or instruments that have two or more parts.
The entire list would be very long, but to give you an idea of commonly used nouns that are always plural we have: pants/trousers, headphones, sunglasses, tweezers, scissors, goggles, and panties. There are other words that aren't necessarily clothing, tools, or instruments but are nonetheless used in the plural: amends, jitters, riches, shenanigans, remains, annals, suds, folk, and cahoots.