Well investors tend to care more about future growth potential than past performance. History tells us that the outlook for expensive proprietary platforms is usually not so good.
I agree and the fall has already started I believe. But they have "believers" that don't seem to understand the rational of people saying this.
Funny thing is that even Steve Jobs said as much in an interview: basically, that a computing platform was dead without market share and they made a mistake with the Mac, making it too inaccessible for too many people.
But I guess history and mistakes are just a cycle.
It would be very good for everyone if they fell from grace and start "losing" profit so they can't start working on stuff, once again.