As far as I know, that's precisely the main reason - or the only reason: the fact that we have ten fingers. I am not aware of any other likely reasons. The decimal system certainly has no intrinsic advantages over other bases.
Quite possibly because humans have ten fingers (including thumbs).
Most likely, early humans, as we have 10 fingers so it is easiest to count in tens.
The history of Roman numerals is not well documented and written accounts are contradictory. It is likely that counting began on the fingers and that is why we count in tens
8 tens 2 ones
340
Lots
Perhaps the ancient men counted on fingers. If we got 6 fingers per hand, many things would be easier - since we have 12 months in year, 12 hours on clock, 12 semitones in musical scale, division of 12 can be done more ways than ten (we can divide 12 in 2,3,4,6 without rest) etc.
by colour coding them and solve them in tens
By ones By twos By fours By eights By tens By twenties By fourty (if you want to count that one)
you pick the nearest number you can count when you count by tens such as 52 rounds to 50 because 5 and under will go to the ten before and 6 and higher will go to the next ten
(400 + 200) - 30 = 570
Mainly because we count in tens. We use the decimal representation which is a way of representing a number in such a way that the place value of each digit is tentimes that of the digit to its right. This probably originates from the fact that we have ten digits (fingers and thumbs).