6'5" and long arms here - and I don't have any trouble with riding a bike with uncut 24" handlebars between cars (not that anyone else should do the same).

Arm length shouldn't have anything to do with it unless maybe your top tube is way too short, causing your elbows to stick way out.

Unless you're build really weirdly, your shoulders (or hips, in which case the narrow bars don't matter) will be the widest part of you, and the 42 cm Syntace bars I just got are narrower than the 44cm bars on my fix are way narrower than the 24" riser (-5 degree for a +/- level stem, for fashion's sake) bars on my ss city bike, to the point of being uncomfortable. In ten years of riding bikes in the city, with bars this wide (or wider), I've never hit a rearview or something sticking off a car, except with a rolled up tube mailer sticking out of my bag. It's the engine, not the machine.

I know some of you are skinnier and narrower than I am, but I know a doofus in Philly who rides handlebars that are so narrow that the ends of his hands hang off the ends of them "so I can get between cars" - he's max 5'4" and his handlebars are easily 4" narrower than his shoulders. And his chain squeaks and is soggy and slack (not to mention his loose headset), so I know that even though he does everything "for performance" he has no idea how to ride a bicycle. Show me an adult that has 30 cm c-c shoulders, and I'll show you someone with a birth defect.

Remember that a cat's whiskers help it gauge what it can get through - and if the whiskers are clipped, it'll get stuck, maybe not at the head, but at the middle part, like when the rearview hits you in the kidney.