Here's why:
* Tuxedo trousers are designed to be worn with suspenders (braces). The high-waisted cut and side adjusters make a belt unnecessary and can even look awkward.
* A belt would interrupt the smooth lines of the tuxedo. The tuxedo is meant to be a sleek and elegant outfit, and a belt can add a break in the flow.
* A belt can be considered too casual for the formality of a tuxedo.
Exceptions:
* Some modern interpretations might incorporate a belt, especially for more contemporary or casual tuxedos.
* If the tuxedo trousers have belt loops, it might be acceptable to wear a thin, non-decorative belt that matches the shoes.
Always check the specific dress code or event requirements. If you're unsure, it's best to err on the side of caution and forgo the belt.