One of the problems is that creating (or just working on) a new framework is a lot more fun and creative than fixing issues in client code. Another problem is that software development is made hard by external factors (read: bad management) but there is this pervasive idea that once we have the right framework (or the right methodology, or ...) then it will finally be easy.

There is enough software to last us forever, but developers have to do something, anything. Creating new frameworks is 'make work', or is used to fleece clients. Or it was in the nineties, at least.