There needs to be a worthwhile trade-in
The last three phones to go out of use went like this:
Huawei V20 - Destroyed when the Missus used it for a Pokemon Go "baby" account and dropped it while trying to play on both hands at once. Well, not "destroyed", but a new screen worth more than the phone was needed. Processed at the local Recycling Centre.
Xiaomi Redmi Note 9 Pro - Donated to the Child, who was now old enough for a smart phone. It does not receive updates any more, but he's 14 and it doesn't matter. The Missus got a Note 12 Pro out of the deal. Which will probably eventually go to the Child when she gets a Note 16 Pro or something. Pokemon is rough on the battery and Xiaomis aren't any awful lot more new than a battery replacement is. Note 9 Pro will probably go in a drawer, being far too old to usefully trade in. My mum can use it when visiting from Canada.
Google Pixel 7 - Ah, here's the one. Google offered a Trade-in Bonus and a sale price on the Pixel 9 at the same time. I didn't *need* a new phone, but swapping a 7 for a 9 for £180 after trade in was too tempting to leave on the table. So hopefully someone is using my old Pixel 7 somewhere. Barring another deal like that, I expect to keep the Pixel 9 for 6-ish years.
So to get a useful trade-in, one must offer a useful trade-in deal. I felt slight guilt at swapping out a 2 year-old phone, but it does pretty much ensure it actually gets used, and paying £90/year to stay updated to the latest seems a decent value.