I’ve added a new page in the Joshua Block Tribute section of my blog:
Class builders help you replace complex and unreadable constructor parameter lists with something more intuitive. While it may add slightly to the runtime of your application due to more function calls, the tradeoff in readability and maintainability is often worth it.
You could even make the argument that replacing a gazillion constructor parameters for some optionally-used builder function calls improves performance.
Or … perhaps builders just help you not pull your hair out when reading code. I’ll let you decide.