@vlogic, my axample, that I’ve seen reflected in Arthur’s comment, is related to targeting elements for interactions.
Let’s say I need to style buttons the same way, except colour. I would create a generic class button and add a specific class for each different colour. Being both global I could target these elements.
But now, I can no longer. They don´t show up in the interactions panel.
This is just o complement Arthu’s well put comment.
Take note that I have no technical training in CSS or otherwise.