Could be used for both. I've used it for generating test data in unit/integration tests and also for obfuscation where production-dumps are needed.

It's useful for having in development as well, when you need to have X number of forms and X number of users but you don't want to have to manually create that every time you re-create the environment.

people use it for building dating sites.

I used this to generate test data for application benchmarking. That is, when I wanted real-ish data to test scalability.

I'm currently using it to mock my API responses for a front-end application.

Writing mock APIs for front-end dev.

So our front-end devs can try their interface designs with different data.

we use it for writing fixtures for tests