P.J. Denyer
Penultimate Amazing
A quick search suggests that between its first and second owners a smartphone tends to last about 6 years, and the common reasons for discarding them are the battery is failing or because they stop receiving updates. So it seems reasonable to think a fair proportion of smartphones will have economic life left in them if replacing their battery is cheaper and easier.
With my optimist hat on, if it's approaching half of phones eventually scrapped because a battery swap is too expensive to be worthwhile, then making that cheaper and easier might save perhaps half of those, for the lifetime of a new battery. Maybe 2-3 years.
So you might stretch the average phone's life from about 6 years to about 6 and a half. That's not peanuts.
Another factor is that a lot of old IT tech, smart phones in particular, is being donated from richer countries where they're obsolete to poorer countries where they're potentially life changing. Making the number of devices that could go this route and be in use for a several years and making it quicker, easier and with fewer destroyed devices when charities refurbish devices for some of the poorest people on the planet seems like a good thing.