If we accept patches, then the person who has submitted the patch owns the copyright on that patch, and that means the software is no longer completely in the public domain. Unless, of course, the patch submitter has filled out a lot of legal paperwork to dedicate their code to the public domain, which rarely happens.

It's hinted in the linked page:

> In order to keep SQLite completely free and unencumbered by copyright, the project does not accept patches. If you would like to make a suggested change, and include a patch as a proof-of-concept, that would be great. However please do not be offended if we rewrite your patch from scratch.

Because they can sell licenses that way and make money off the product.

Tight control? Consistent vision? Less overhead? All of the above?