So, reason is not important. Important is problem.
But if you want to know: (1) result is required for further computation purposes and (2) for formating.
The reason is always important, especially when people don't seem to exactly know what they are talking about.
Showing the number of decimals is definitely not something to please the eye. It is showing the accuracy of your value, so a value of, say, 100 (metres) measured up to a mm is correctly shown as "100,000 m" whereas the same value with an accuracy of 1m is shown as "100m".