Not everyone wants to root their phone and most of those stock android ROMs are pretty terrible compared to official touchwiz ROMs, for various reasons. For example, CODEC support is worse, never mind I hate the stock Android UI. Also need the Official JB update to add features Samsung/AT&T ripped out in the ICS update, like WiFi Synching to Kies.
They really should be fast-tracking this update because this phone is borderline unusable on LTE with the current battery life. I really wish I could go back to an HSPA+ device at this point, because having a phone go from 90% to 40% in < one hour of use (web surfing and texting) on LTE makes it almost worthless as a smart device.