But that doesn't tell you whether it's important. Statistical significance is a measure of trustworthiness, given assumptions about the generating process. It tells you nothing about whether the data is in any way meaningful, after assuming relibility.
What does tell you about that type significance of (rational) data is the delta, which requires the 0 in order for you to see the scale. Now, in many interesting cases this could be represented as error bars under H0, but that's usually not done in publications, because they only have room for one plot type.
The range of the plot is not arbitrary. To suggest otherwise is deceptive.
