You could compare it to people writing CSS, JavaScript and Markup in separate files Vs having just one file in React/Svelte etc. which gives the user the option to combine everything into one.
There maybe a lot of drawbacks from the latter approach but it's makes everything a hell easier for people to just get started building.
As far as building something fast, I'm with you. I always reach out for Python with UV, Litestar and Advanced Alchemy when I want to build personal web projects. I don't think SQLC is bad as such, once you've written your SQL you can essentially compile that into a CRUD application which is ready to go. As you've pointed out, however, you'd need to slam something like a GraphQL engine on top of it if you wanted rich quries easily, and you'd still not have the auto-generated OpenAPI that comes with Python web frameworks.
SQLC is for code where you want a low amount (or zero) external depedencies. Which is a very "Go" thing to want. It does scale well, but that requires you to build various CLI tools to help maintain things as well as your own Go modules to add "quality of life" like dynamic routers and get queries for low traffic requests.
I'll try SQLx eventually when I get time to look more into Rust.
And of course now that I have it, the incremental cost of adding a new query is really low as well