The issue here is the vast majority of people dealing with cryptos don't know what micro and milli mean. I can't count the number of times people look at me dumbfounded because they can't convert between the amounts because they don't know basic conversion. Anyone who has been to elementary school should already know the meaning of micro/milli, but sadly that just isn't the case. "Bit" takes away this "difficulty" people often have with trying to figure out the values.
Anyone who doesn't know metric prefixes will not know what a bit is. Why introduce an arbitrary definition when the metric system or satoshis work perfectly fine? Seems like adding difficulty to me.
Well, people like this idea of what is "easier." The fact that milli and micro are even PART of the word turns people away because it turns into science. At the end of the day we're not going to be able to cater to everyone. For me, I can simply remember that a "bit" is a uBTC. It's not a huge deal for me either way. It does bring up a question, though... would it be like:
Bit (uBTC)
Megabit (mBTC)
Gigabit (BTC)
Or what? *That* is where it gets confusing.