Of course if he wanted to buy a loaf of bread in the future with Bitcoin but each bitcoin was then worth $1 Million each, if it weren't divisible to 8 decimal places then he would have a problem buying the loaf of bread for the bitcoin value it was worth.
So if the loaf of bread today is .001 bitcoin then it ten years the equivalent value might be .00001 bitcoin.
I think we will all be glad that the magic exists if it didn't then we would have to buy the loaf of bread for $1 million bucks.
Also to think that 21 Million coin cap without the divisibility would somehow be enough for the "world" to use as a serious currency alternative is naive .
If Bitcoin in the future was adopted on mass and if there was ever an issue of not enough decimal places or alternatively the 21 Million needed to rise for some technical reason I'm sure thru consensus and planning it can be forked to do this for the right reasons although would by then be a nightmare to do this.
The main issue with crypto adoption for some users will be the quirky long address names, making mistakes using them, possibly losing their money and making payments with decimal amounts.
The software needs to improve and get easier in specific ways.
We think in whole amounts when trying to access the value of things and often use our weeks wage or salary to gauge that value and now with Bitcoin we have to adjust that reference but it is hard when the value of Bitcoin is likely to change so much.