For example, if I am buying a $5 coffee, it will cost 0.0033 BTC now... Too many zeros behind the dot! Isn't it better if we use 3.3mBTC for a coffee? At least this is easier for someone with poor math like me...
To be frank, it really doesn't matter.
People in Japan are used to quoting prices in thousands of yen. They don't freak out when the price is quoted in dollars, and it is only a few dollars.
It will make absolutely no difference, given the extent to which Bitcoin is divisible.