Because agents can build things, but fortunately for us humans, there's still room for making sure the "right" thing gets built.

i.e. why read a book written by a human when an agent can write one? Why buy a painting that could have been printed.

One of the benefits of open-source and frameworks is they're made up of battle-tested decisions by a lot of people with real skin in the game for a long time. Yes an agent will often solve your problem, and will solve it correctly - as asked, but often a better answer is found by stepping back, evaluating the fundamentals, checking other perspectives, challenging assumptions, and having an opinion.

Having a framework as guardrails (Hah!) for agents is still very powerful, in my experience working with Rails + Claude it works together really well and there's not really a downside compared to doing it completely from scratch.

I'd rather point the agent at and authentication gem and tell it to use that, vs telling it "build authentication, make no mistakes".