Why should everyone have access to draw.io and diagramming, and not just the graphic designers?
Diagrams help explain things in a way that words can’t. And those things (processes, etc…) will effect everyone - not just the designers.
On the flip side, everyone has to explain something at some point in their lives and/or careers. Having access to a powerful yet easy to use diagraming tool will help everyone to explain the thing that needs explaining.
For example, I used draw.io on Confluence to explain a relationship between original orders and change requests within Salesforce.