Given how Android's been doing in terms of phone market share, I don't think Android OEMs need to be too terribly worried that failing to provide updates is seriously affecting their long-term viability. At least not for the moment. These kinds of complaints mostly only crop up among HN geeks like us; the bulk of the market at large doesn't know about, doesn't understand, or doesn't care about the issue.
On the other hand, paying for the development resources it would take to supply those kinds of updates would force an OEM to raise their prices. For reasons related to the above, It's reasonable to surmise that would be a suicidal move for any Android OEM. None of them are fueled by customers who love that company's product so much that they'd be willing to pay a premium price for it. On the contrary, the Android market is characterized by heavy price competition and razor-thin margins. It's like the PC market of 10 years ago: There's simply no mercy to spare for a company that blows any significant money on happy-warm-fuzzy customer support.