why do you care about fixed vs variable costs?

So it looks like some people are curious about how a company divides its fixed costs and variable costs between things like COGS and SG&A. Is this so they can figure out how much incremental revenue would affect the company's EPS. It seems like this topic is related to something called "operating leverage". Can anyone else share anything on this topic? 

Added context would be is this something investors ask company's IR team to figure out