What difference does it make if they are from the past. They are produced and shipped today, components have to be updated, they are sold today, their supply chains have to be managed today, iOS has to run on them today, they get the same warranty and customer support that 6 and 6 plus have. Right now, 75% of their phones are NOT 6 or 6 plus. It takes people and focus to do all of this.
EDIT: The way you are talking about 4s it would seem Apple only has a design team, once something is designed everything else happens automatically.
> It's not like Apple is refining the 4S and coming out with new versions of those devices.
Actually, they are. You think the BOM hasn't changed? You think it's the exact same components being shipped from the exact same suppliers?
The specifications are the same, but the components are newly manufactured. I'm sure the BOM has rev'd. It's a mistake not to consider phones as part of their lineup which you can buy new, just because they have lesser specs and were initially released a few years ago.
I think this is an important part of Apple's strategy, which comes specifically from the way they maintain iOS, which other vendors have largely missed out on.
Google only has one phone because that phone isn't even supposed to make money. It's a phone meant for Android developers both internally and third-party. Google may not lose focus from all the other handset manufacturers creating the thousands of different Android devices, but they certainly have a difficult time with integration.