One benefit is when working on multiple code bases where the size of the code base is larger than the time spent working on it, so there is still a gap of knowledge. Agents don't guarantee the correctness of a search the same an old search field does, but it offers a much more expressive way to do searches and queries in a code base.

Now that I think about it, I might have only ever used agents for searching and answering questions, not for producing code. Perhaps I don't trust the AI to build a good enough structure, so while I'll use AI, it is one file at a time sort of interaction where I see every change it makes. I should probably try out one of these agent based models for a throw away project just to get more anecdotes to base my opinion on.