I can think of a couple. I'm not sure if either one is enough to overcome the incentives to do otherwise, though.
1. General brand goodwill. If it's known that the phone you buy today will be functional for the next 5 years, then long-term customer loyalty may incentivize a company to make sure their units last that long
2. App-store market share. The longer your phone lasts, the lest likely its purchaser will replace it with another ecosystem's product. This would increase the lifetime revenue you get from that buyer.
Again, I'm not sure if these two incentives are enough to outweigh the "new every two!" hardware refresh profits.
1. General brand goodwill. If it's known that the phone you buy today will be functional for the next 5 years, then long-term customer loyalty may incentivize a company to make sure their units last that long
2. App-store market share. The longer your phone lasts, the lest likely its purchaser will replace it with another ecosystem's product. This would increase the lifetime revenue you get from that buyer.
Again, I'm not sure if these two incentives are enough to outweigh the "new every two!" hardware refresh profits.