A new survey from mobile operator Vodafone UK has claimed that people are now keeping their mobile devices for longer, with the majority upgrading every 4 years
Devices are prohibitively expensive these days. The marginal gains from improved tech is also not used to benefit the end user. Devices are not working for the one that pays for it.
If only they would release a flagship device with unlocked boot loader, open drivers and a pledge to support it for 10 years. I would buy that. Otherwise I see no need to upgrade.
It's less that the improvements are marginal (modern flagships are significantly more powerful than 4 years ago for example), it's just that 90% of people have absolutely no use for most of that increased power. The most intensive thing most people do on their phone is watch media.