Is it true you could be banned for putting ads on all of your pages on your website? I would appreciate your help on this topic.
Google wants you to put ads on as many pages as you can.... more pages with ads = more impressions = more clicks = more earnings for Google (and you). As long as your pages are not violating the TOS, you can put ads on them.
You can run AdSense ads on each and every page. Just make sure you have some content on that page as well. Running AdSense on sites under construction or with little to no content at all is not recommended. By the way you should read the Google AdSense TOS at least one time. Everything is explained there.
and why should google do that?Maybe you misunderstood with the number of ads allowed per page..You can check Google Adsense Programme Policies for detailed information.