There's a lot of economic pressure against building new systems. Making new hardware and software takes longer than building on the existing stuff. As time goes on, it gets harder and harder to match the features of the existing systems (imagine the effort involved in reimplementing a web browser from scratch in a new system, for example), not to mention the massive cost benefits of manufacturing hardware at a large scale.
Many people working in software realize the systems they use are broken, but the economics discourage people from trying to fix them. Is it possible to fix the economics? Or maybe we need more people able to resist this pressure?