The argument is a bit like saying decimals are wrong because the one in "10" jumps to one after you counted to 9, which is 90% of the range and not 50%.
But that is the point of using multiple digits. Similarily the point of using multiple units of time is that each of the parts is in it self correct. 15:30 always means it is after the 15th hour and after the 30th minute.
If you want to know it more precisely you either wait till the minute changes or you get a clock with seconds. With the proposed system you would not know if the time is before or after the 30th minute. Also: why stop at the minute? You could also round the hour.. But that would introduce a weird jump and the minute would suddenly be negative 30.
But that is the point of using multiple digits. Similarily the point of using multiple units of time is that each of the parts is in it self correct. 15:30 always means it is after the 15th hour and after the 30th minute.
If you want to know it more precisely you either wait till the minute changes or you get a clock with seconds. With the proposed system you would not know if the time is before or after the 30th minute. Also: why stop at the minute? You could also round the hour.. But that would introduce a weird jump and the minute would suddenly be negative 30.