I'm having trouble understanding what you mean.
I mean, you don't go to the store and have them expect you to figure out the price of the product, taxes and exact change by yourself.. you know?
Why would it work any differently with Bitcoin?
If you're doing a friend to friend transaction most wallets tell you the price or you can look up the exchange rate yourself.
For example, what if you were in a Coffee shop, and the cup of coffee costed .000125 BTC
The average person would not want to waste time squinting at the decimal places and figuring up how much it actually is. Of course this is just my assumption that ordinary people would not want to do the math in their head all the time. I am decently intelligent and even I have to stop and think about it sometimes.
The problem isn't with the decimal places. It's because you're trying to value bitcoin against another currency. If you always used bitcoin, and know that starbucks sells coffee for .000125btc, macdonalds sells coffee for .000120btc, and so on, if you learned to value things in bitcoin, you don't need to do any math. You just intuitively feel how expensive or cheap it is.
On the other hand, if you go on vacation and use chinese yuan or japanese yen or something, even though the number of decimals is the same, you still need to do some math in your head to get the USD value or euro value or whatever currency you use.
It's about how used to the currency you are, not about the decimals.