The point is that you may have a really good app that users want/need, and which presents ads, but in some unobtrusive way that users don't mind.
If you don't put in "anti-ad-circumvention" methods, then the ads will fall victim to some simple blanket blocking scheme that users set up before they even installed your app, not targetting your app specifically.
Analogy: a website with great content and very unobtrusive ads has them filtered by AdBlock anyway.
Currently the people who block in-app ads are people who have taken the effort to root / jailbreak their device. I find it hard to believe that they would put up with the ads.
