This is typical of software development projects - the "new" replacement wants to kill off the old one so cannot have any improvements happening to the old one.

This is typical of software development projects - the "new" replacement wants to kill off the old one so cannot have any improvements happening to the old one. If the new ones are so great though ..... I suspect that quite a lot of maintainers of code don't want to rewrite it particularly and quite a lot of people upstream of that don't want to re-integrate everything to use something new. So little improvements that can be taken a bit at a time are fantastic.