A few reasons:

1. Unlimited projects: when you spin up traditional backends, you usually use VMs. It's expensive to start many of them. With Instant, you create unlimited projects

2. User experience: traditional CRUD apps work, but they don't feel delightful. I you want to support features like multiplayer, offline mode, or optimistic updates, you'll have to write a lot more custom infra. Instant gives you these out of the box, and the agents find it easier to write than CRUD code

3. Richer features: sometimes you'll want to add more than just a backend. For example, maybe you want to store files, or share cursors, or stream tokens across machines. These often need more bespoke systems (S3, Redis, etc). Instant already comes with these out of the box, and the agents know how to use them.

There are a few demo sections in the post that show this off. For example, you can click button and you'll get a backend, without needing to sign up. And in about 25 lines of code, you'll make a real-time todo app.