Not sure trying to torture the ’worthwhile use of debt’ answer out of dupont is appropriate. But that doesn’t mean the extra 2 steps don’t give insight.
Using EBIT rather than NPAT removes the financial structure influence from the profitability component which gives you a better economic insight and makes it much more usable for comparing across companies with different financial structures.
Isolating Interest/Assets a component is useful. It’s the jump of point to consider a company’s cost of debt and also how much leverage is not interest bearing.
In deciding the worthwhile use of debt question, you have to first answer the question, is the company's use of funded capital economically profitable, then you can look to the efficiency of the financial structure.