True. The article has a decent answer though. Incremental builds are necessary because:

> [Slow builds] can be annoying if your site has 1,000 pages and one content editor. But if you have say 100,000 pages and a dozen content contributors constantly triggering new builds it becomes just straight up impossible.

Gatsby needs a cloud to host this build server. They also apparently host a nice content editing UI.

If you don't need a content editing UI, and/or are fine maintaining your own static builds, you presumably wouldn't subscribe to the cloud service.