reported in https://forum.matomo.org/t/auflosung-der-graphen-erhohen/37766
it might make sense to do this after #16120 (or this might even already be the default of c3.js)
All line-plots in Matomo start their y axis at 0 and end at a sometimes arbitrary maximum. The issue is that there are a few graphs where variation is small (especially the average page generation time) and therefore the plot only shows a horizontal line:

So no pattern is visible. For comparison, the default output of Matplotlib for the same data: (of course this is limited by the fact that the data in the API is only in 0.01s resolution)

We can clearly see that there was an increase at some time and there seems to be a weekly pattern. So providing a way to not have every plot start at 0 provides additional insights.

Of course making this the default might also be an issue especially with people who don't know how to read plots and might see pattern in random noise.