I feel like a belt ruins the appearance of many pants, sometimes you just don't want a belt with your outfit. I like to focus of finding pants with a good fit, and take them to a tailor for some modifications if necessary.
It really depends on the outfit/aesthetic. Some outfits are very much ruined by a belt and others will look very "weird" if you aren't wearing one.
Everyone's different, but I find that cargo pants and shorts look very much "I used to wear my phone on my belt" if you wear a belt. But jeans, slacks, and outright suits look REALLY weird if you don't have that bar of color dividing pants and shirt.
Although, if you are wearing a more "outdoorsy" outfit (e.g. you shop at REI) then I find the belt very much becomes essential for aesthetics again.