I think you would. It's hard to see from the perspective of using another language, because you don't think of the code you write as emulating sum types.

For example, in my biggest F# project I parse a local standard for public transport timetables. In that format a trip can either drive through a stop, drive around it or stop there at a particular time. With a sum type, I can represent all three of these cases without worrying about a value of that type having both "driving through" and a time set. When you've got a language that effortlessly allows something like this, you'll find uses for these paradigms.