So my personal experience makes me doubt that my phones are some kind of exception. These things seem to be plenty durable enough to last several years. I think there's not as much difference in hardware and software as you'd like to think.

If you want to make definitive statements, then I have to ask for your data.

Some basic searching I've done unearthed a paper[1] in the Journal of Industrial Ecology[2] that concludes that economic lifespan (how long a phone is actually used and thus depreciation rates) is only marginally effected by the functional durability (including hardware and software quality). Instead, they suggest that lifespan is more effected by brand equity and related intangibles. People choose to use certain products longer regardless of whether other products have similar functional qualities.

Thinking further on what could cause intangible factors to have such a large impact on the secondary market and depreciation, I can't help but wonder if each brand is attracting different kinds of people with commensurately different attitudes towards their smartphones. That certainly could drive a difference in behavior, and could even be a self-reinforcing trend where the users more likely to retain their products longer are drawn to the brand with the users who are more likely to retain their products longer.

This would mean that the S5's and S6's I've been talking about aren't the exception to the trend. Their users are the exception. That's something I'd be happy to accept. There definitely is a difference in behavior between iphone and android users.

P.S. it's worth noting that the paper itself was seeking to determine if repairability would significantly increase the economic lifespan of smartphones. That's why they were looking at what factors caused people to use their phones for longer or shorter periods of time.

[1] https://onlinelibrary.wiley.com/doi/abs/10.1111/jiec.12806

[2] https://en.wikipedia.org/wiki/Journal_of_Industrial_Ecology