Carriers have absolute control over the consumer sales channels, and that gives them all the power. The carriers demand extreme control over the hardware and software pushed through those sales channels, and the manufacturers (other than Apple) have no choice but to give them that control because that is how you win in this business. Just ask Samsung, who made $5 billion last quarter selling devices running outdated Android 2.x. Or ask HTC, who got crushed by the carriers after offering devices with unlocked Android bootloaders.
If you're a manufacturer, you win by being the one who makes the carriers the most money per customer per month.
So how does ICS help Samsung make more money for Verizon? How does upgrading old devices to ICS help Samsung make more money for Verizon? If you're Samsung, that's the only question you're trying to answer.
The reality is that ICS does not help Samsung or any other manufacturer make more money for Verizon, and that's why ICS adoption has been so low.
The problem is that the manufacturers (other than Apple) have little desire to change this business model. If (and when) Samsung begins to defy the carriers, LG and Motorola and HTC will trip over themselves to take Samsung's place and become the next darling of the carriers.