Fewer and fewer car companies are making cars with manual transmissions. Even in the low-end.
Why?
Customers, as a whole, don't want them.
It's the same thing.
BTW, you raise this issue, Gav... but let me ask you... do YOU a manual focus lens? Have YOU researched the ones available to see if they meet your needs?
Also, let me ask you another question... you seem to be asking for manual focus, but you want image stabilization and advanced glass and materials. Why? Why do you want all the benefits of so many other technologies but then do not want the benefit of what is probably the most commonly available one? Esp. when you can (as someone else pointed out) just turn it off?
As Amolitor suggested... there's also costs. What makes you think that production of a lens with all of those capabilities but WITHOUT autofocus will cost LESS? Fewer of them will likely be sold. That means that the R&D costs will be passed on to fewer consumers, potentially making the cost the same... and potentially even making them cost MORE.