There has not been a need to update every two years for many years. And there is far more waste from lower quality products that last fewer years.
Now even if Apple hears people cursing them and grumbling on forums, the fact that they keep on buying their product means that it's not enough of an issue for them to stop buying it.
Point being, given the enormous amount of raw materials it takes to make a phone, and the environmental damage that comes from extracting them, I wonder if it’s a good idea to be cavalier and see it as a “rounding error.”
Just because you wish to be a careless consumer doesn't mean that that's what everyone is and that we shouldn't put pressure on Apple to allow those that don't to use their devices as they wish.
A Juniper firewall is an appliance.
A NetApp SAN is an appliance.
An Ooma VOIP phone system is an appliance.
A Kindle is an appliance.
A Nest thermostat is an appliance.
These things are not general purpose computers. They are custom fabbed hardware with vendor supported software and are not user repairable. They do one job and they do it well. At the end of their service life you replace them.
My iPhone is an appliance and I prefer it that way.