In creating the histograms, two aspects of the information contained in the original data are lost. First, the time order of the observations are not reflected in the histograms. Second, the histograms show only how many days on which stocks attained values in various ranges. The actual prices on those days are not shown.
Histograms present large amounts of information in a very compact form.
It is much easier to compare price series based on their histograms than by looking at almost 1000 numbers for each of 10 companies.