Finance, economics, ecology, virology, electrical engineering, mechanical engineering, chemical engineering, software engineering, pretty much any field with a

Finance, economics, ecology, virology, electrical engineering, mechanical engineering, chemical engineering, software engineering, pretty much any field with a technical component (i.e one that uses numbers). You could reasonably just look at 2^n for software, though in general usually continuous math is simpler then discrete math IMO. Doubling vs. e^x is kind of an exception to the rule, and if you do any software involving signal processing or simulations, you'll want to understand the continuous version.