Wrong. AT&T (and other phone companies) continue to limit and throttle their data usage. Wasting precious data on worthless ads is an extremely valid reason to block them, especially when traveling abroad where data runs at an extremely high premium.
Privacy is another. iAds are targeted and collect data about your iTunes purchasing history, location data, and any other download or library information they can gather to determine what ad you see. Many people are not comfortable with this form of privacy invasion, which makes for yet another great reason to block ads. You don't know what information they are gathering, you are not notified, nor can you opt out of this collection. Regular apps have already abused the collection of data and contacts and ad targeting will do the same if it hasn't already. You can install a firewall on any computer, ad and script blockers on any browser and you should have the same control on your phones, where most people store significantly more private data than they do anywhere else.
If there will never be a valid reason to block unwanted ads on your phone, then that means there would never be a valid reason to block ads on your TV, your computer or websites either. But we all know that's not true, because there are plenty of valid reasons.
Stop making excuses for lazy developers. If they want to make money with their app, then make a good app and people will throw money at them to get their hands on it.