Mike Cisneros lays out the argument:
In school, I was taught that you should center-align and capitalize the first letters of words in titles. I’ve noticed, though, that storytelling with data charts only capitalize the first word in the chart title, use ALL CAPS for the axis titles, and don’t center-align anything. Why?
Title casing is a really hard habit for me to break. I understand the “why” behind this, but it’s a change I’m unlikely to make anytime soon.