You can see this with Microsoft products. Microsoft has to have its updated products compete with its previous products.
This is also true of Project Xanadu. If we consider the Web as an early form of Xanadu, we can see that it was released prematurely. There are lots of design flaws and over the years band-aides have been applied to them. There are still many people who fight against these band-aides (I'm looking at you IE6 users and corps who force the use of that browser). We're stuck using hacks for what should be easy. People are now used to do things the hard way and using hacks and cannot easily envision a system that doesn't suck.