It provides a good comparable baseline for all candidates.

Reviewing tests and points in open questions. A good set of predefined questions. A lot levels and languages.

Clean experience for coding interviews - a great compliment to phone, and perfectly real time. It allows the interviewer to prepare questions and templates, and it enables the candidate to write in any language of their choice. It has just enough functionality for organizing interview questions and candidate responses, and remains lightweight and easily usable for the candidate (who is often a first-time user).