Motivation
Sometimes users might not be using uv. For now, a flag like --no-install for tools could be good: for example usethis tool ruff --no-install would add config only. That way, they could still get many of the benefits of getting config right.

I am not convinced that --no-install is a good name. If the user isn't using uv then ideally we would give them advice on how to install it with other means (although identifying the correct means might be tricky. Conda? Pip? uv?). The --no-install name implies the user is self-consciously not wanting to install the package, but that's not quite right - it's about not wanting to use uv in particular via usethis (they may still want to use uv with another means or install the dependencies with another tool). Note that the dependencies might not be obvious so an explicit message is probably a good idea.

Another possible name might be --no-uv but I'm not sure I want that in the interface long-term, and I'm also not sure it really communicates the fact that this will result in an uninstalled tool, i.e. it won't be ready to use.

It's worth noting that uv wouldn't be called in the first place if the dependency is already declared in pyproject.toml. Also, would we still add the dependencies to pyproject.toml, or only not install? That also impacts the choice of name.

Summary of desired enhancement
Consider what this flag might look like and implement it.