This likely isn't targeted at you, dear audience -- odds are that you've already got the discs for WoW, and if you do buy a new PC, you'll probably still delete WildTangent's app and install WoW yourself. Instead, it's a stab at picking up new subscribers -- people who might not already know about World of Warcraft or PCs may see the icon on their new desktop, double click it, and find Azeroth for the first time. The press release even notes that WoW subscribers still in their trial month are counted as subscribers, so odds are this is a random attempt to pick up a few more subscribers from people who aren't willing to go get the game themselves.
There's one more thing to note here: Activision isn't mentioned at all.
While those familiar with WildTangent and the perception that their software is junkware and bloatware may suggest that Activision is somehow behind this deal (sneaking software onto new users' PCs definitely seems more up Activision's alley than Blizzard's -- the former company has gotten a reputation for releasing only slightly updated sequels constantly, and the latter has instead always been consumer-focused, even releasing Mac and PC versions of its software on the same discs), the press release specifically says Blizzard Entertainment is behind the deal, and only mentions Activision Blizzard in the company summary at the end. So who knows -- maybe Blizzard is feeling pressure to keep that subscriber number rising, and is willing to resort to a deal with WildTangent to try and pick up a few more players. Whether that tactic will work or not remains to be seen.