In marketing terms those metric prefixes sound very small and evoke the suggestion of dealing with tiny little fractions. Though I'm not much of a salesman, but arriving home and telling your girlfriend or wife, or both, you bought 100 milliBitcoins for $80 would not impress her and make her think of you making a great investment. The story turns 180 degrees when you tell her that you bought 1000 rootBitcoins for $80, doesn't it? Additionally there is no need to name each increase by the factor ten/hundred/thousand; nobody writes 1 gigaDollar or 1 megaDollar or 1 kiloDollar or 1 deciDollar.
Yeah, I agree that those metric prefixes don't really "sound right" when talking about money. I was an electronics tech for twenty years, so I'm accustomed to the metric prefix terminology when discussing millivolts, kilowatts, picofarads, etc., but it just doesn't seem quite right when talking about money. I'm not sold on "rootBitcoins", but I'll go along with whatever term most in the community go with. I don't have an adamant opinion on it, just tossing some ideas around.
As you know, bitcoins are very different than fiat currencies and there is less of a need for metric prefixes when discussing them because bankers just create more of them before they have a chance to appreciate in value ("deflation" they like to call it). If the dollar supply had been controlled over the last hundred years the same way the bitcoin supply will be controlled for the next hundred years, they would have been forced to redefine the currency units (similar to a 10-for-1 stock split) or something along those lines.