The three most common reasons:

  1. Professional design. They want their app/site to look polished and professional. They are looking for nicely-designed UI components and there are tons of developers who want to build stuff, but who don’t have a design background. Rather than spending years learning how to design, why not use a third-party package that provides beautifully-designed components right out of the box? Limits: Having high-quality bricks is necessary but isn’t enough, you also need to know how to use them, it’s still your job to assemble them.
  2. Saving time. They want to get something up and running quickly without spending a bunch of time building everything from scratch. Building a whole component library from scratch is a significant undertaking and one that can be skipped by relying on a UI framework. Limits: Many of those who pick our UI library also do it because they also lack the frontend skill necessary to build the components themselves, they are not learning how to use the platform, leading them to sometimes spend more time trying to bend a component for a use case it wasn’t designed for rather than creating a new one from scratch.
  3. Usability and accessibility. They recognize that many UI components — things like modals, dropdowns, and tooltips — are really hard to get right, especially when considering accessibility, so they want to make sure they get it right. Limits: Nobody should be building a modal from scratch at our age, but you also want something as lightweight as possible.

Benchmarks