Mostly? DSLs and templates. The goal of an in-language DSL isn't necessarily to feel like you're writing that language (I wrote a DSL once that made it easy to generated shared enums for C++, C#, Java, and Ruby. It was Ruby behind the scenes, but because it was declarative, it didn't feel like Ruby. Additionally, the templates used to generate the resulting code almost exclusively used for loops.)

I almost exclusively use the #each-ish in my libraries and in the backing code for such DSLs or templates.