Part of the problem is that most startups run with zero revenue for the first few months (or longer). Generally speaking, if you have no revenue then burn == e

Part of the problem is that most startups run with zero revenue for the first few months (or longer). Generally speaking, if you have no revenue then burn == expenses. So for the period during which most founders are starting to learn about these terms, "burn" and "expenses" are indistinguishable. That tends to cause them to think of them as essentially the same thing for far longer than they should.