A lot of people are blaming apple for this.
I blame their users and their loyal fanbase, who, predictably, complain each cycle about something like this, and there is often a lawsuit. Whether it be that instance where the phones could be bent or this one where an update is trying to preserve the battery life that they've been using hard for 3 years. They'll complain, some of them allegedly swear off apple but by and large you see them next time around, having gone right ahead and bought the product they swore off.
If Apple is doing this to get people to move to their latest phones, I don't blame them, because it seems to work. People by and large buy iPhones for the status, and that applies double when it's the "latest and greatest" model- they aren't a product that tends to get used beyond it's sell-by date because when the next one comes out it's no longer cool to have.
Mind you- Throttling performance to preserve battery life with aged batteries seems like the sort of design-oriented decision Apple might make anyway.