As your application gets larger it's not that easy. Even if your code hot reloads all the time, getting to the piece of code that breaks might take 10 clicks or you are working on some feature that has quite a few combinations for use and/or settings that influence it. Maybe some feature flags thrown in. With this setting off and that feature flag on, suddenly your integer is a string. Boom runtime error but only because your QA thought of it when testing it 3 days after you already moved on to another ticket.