I'm going to differ slightly on that. A business should be providing a product that reflects the needs of their customers, and not the other way around. Now it's entirely possible that the number of Kobo customers using XP diminished to the point that supporting XP via Kobo Desktop was no longer cost effective. If they dropped XP because of that, it's a good business decision. If they dropped XP support to pressure XP users to move on, that stinks of a poor business decision because their responsibility is to serve the customer as long as it improves their bottom line.

(Microsoft's support of XP is an entirely different situation since they have a vested interest in selling updated products and reducing the support costs for older products.)