Because they're dumb cartoons. Unless we're talking about a Smurf, because then, well, they're simply required to wear pants by law.
It is especially OK for really hot chick cartoons like the ones featured on the Top 10 Pantsless Moments on Adult Swim to run around nekked.
But why the FCC will allow animated fat guy junk on cable but not Janet Jackson's perfectly sculpted naughty bits is beyond me.
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