Perhaps the intended use isn't for production-level designs are for rapid high fidelity prototyping?

Or perhaps specifically for junior designers that want to learn by reverse designing.

Just a thought.

They can be a good starting point with projects where the components are easy enough to resize and restyle to your liking. Especially with Sketch where UI Kits can be smarter. Components use global styles so updating 1 button would update everywhere. This makes it possible to enhance/change the original style or remove them completely for low fidelity.

They can essential save a lot of that initial time you would typically spend in having to draw everything from scratch and setup the document styles, naming conventions and so on.

But, they're not for everyone of course. :)

I agree. I’ve downloaded these before and they’re often inappropriate for any projects. Why? Because each project has a different aesthetic. Even if it’s a tiny difference, these UI kits will look out of place.

I see them as a good way for people who don’t design to create a an interface. Much the same as Twitter Bootstrap.