Why are most bar graphs of a one-shot measurement empty?

During a one-shot measurement, there is only one reading for a certain observed quantity. Most bar charts symbolize how much a measured value differs from the previously observed measurements, however.

Since there is only one reading, there are no previously observed values, i.e. this measured value is both the minimum and maximum of the observation period at the same time. In this situation, it does not make sense to present any value in the bar chart.