Verizon is over-rated, they want premium prices for their old CDMA technology, plus their data network is slow, i would never buy a smartphone from Verizon, unless their network was as fast as ATT's and you could make phone calls simultaneously while surfing the web without Wi-Fi.
Verizon may be over-rated for YOU, but as you know service quality is very Geography-dependent. For those of us who live in an area where Verizon service is better than AT&T, it is not overrated.
As the Wall Street Journal reports today, Consumer Reports has (consistently) rated Verizon's network superior to that of AT&T. There are many places where AT&T is better than or at least as good as Verizon. That ain't the case here in the San Jose area, where my Verizon phone consistently has good service and I have at most one bar on my iphone.
Apple is simply making a good business decision to prevent itself from losing more ground to Android and to selling to consumers who want Verizon.