It gives them some pride and if you turn a huge profit you will have respect for that person. Not all people are evil and when it comes to making money with Adsense they can giveaway all of their secrets and Half the people that actually listen won't do everything that they need to to make it work, and on top of that you actually need to get a fair amount of visitors to make it work.
If you really want to make money, drop Adsense like a bad habit. Seriously. Adsense is garbage unless you have a really high traffic site which most of us don't. AdBrite is your best alternative. They don't put a restriction on how many ads you can serve per page so you make 3 times what you would make with Google's 3 little ads per page.
I'm glad to say that not only have I posted pics of my check, but I have detailed exactly how I made the damn money as well. And you know what still pisses me off? When people pm me or write in the post how I did it?!?! I mean c'mon did you even read the blog post?!!?
It's evil to keep your business practises to yourself? Go ask Shoemoney for his websites and how he makes money with them, he'll ignore you. People who have secrets worth keeping don't share them publically. It's suicide.
You can always create new niche sites, so really competition is not an issue. The internet is growing constantly, and so are its users. What competition are we talking about? As long as you have good content and update daily, visitors will come your way.