Generators produce something from nothing: strong passwords, UUIDs, QR codes, placeholder text, sample data for testing, colour schemes, or slugs. They remove a small but recurring blocker when you need a value and do not want to invent one yourself.
Randomness quality matters more than it looks. Password and key generators should use the browser's cryptographic random source rather than a simple pseudo-random function, and should never transmit what they create. For test data generators, the useful ones let you shape the output, choosing fields, formats, row counts, and export as CSV or JSON so the result drops straight into your fixtures.