A logarithmic scale is used to show the magnitude of some values, not their absolute value. The "distance" (in that case measured into the y-axis direction) between 1, 10, 100, and 1000 is the same. In comparison, using the usual linear scale the distance between 100 to 200 and 200 to 300 would be the same.
The intent is to flatten out peaks. Also, all your senses as a human being measure the environment in logarithmic scales - hence it is more "natural".