Apple's own history does not offer any assurance to investors.  Apple revolutionized the personal computer with the introduction of the Macintosh.  Despite having first mover advantage for quite a while, Apple failed to secure a significant position in the personal computer market.  They were nearing bankruptcy when Steve Jobs returned to resurrect the company.  

If you attribute Apple's troubles in the personal computer market to the company's ethos in general or to the absence of Steve Jobs, it may appear as if history is repeating itself.  Indeed, many observers and investors feel that this is likely what is happening, perceiving Apple's path from success to near-bankruptcy in the 90's to be a warning of what is to come.  History absolutely has a role to play in how the market is currently valuing Apple (regardless of how misleading it may be).

Lately there has been a popular view that Apple's refusal to go for market share by selling a cheap iPhone will result in dominance by Android and marginalization of iOS (and this time Steve Jobs will not be able to return to save the company).  Recent figures that have Android holding 80% of the global smartphone market are cited to support this view.  This narrative coupled with the history of personal computer industry make a superficially compelling bear case that has convinced many observers.