This might be one to check on Snopes, but I've heard that asparagus affects everyone's pee that way and makes that odor, but only about 20% of people can smell it. Most of us aren't going around smelling other people's pee so we just assume it's affecting our own pee and not other people's when they say they don't smell anything. Presumably it is making their pee smell but they don't know.
Sadly, I'm one of them cursed with this sense of smell.