Google Adsense has very high standards and they maintain it by continuously reevaluating their existing features to ensure effectiveness of the product as a whole. It looks like “Onsite Adveriser Sigh Up” feature, which allowed advertisers to sign up for Adwords campaign directly on your site, wasn’t performing very well, because Google Adsense team has decided to gracefully retire this feature.
They rather believe in supporting and developing the features that drive better monetization results for publishers. Even if that has to be done by retiring some previous features like advertiser sign up on site.
I think many publishers have made links that actually lead to some customizable Onsite Advertiser Sign Up page. News is that all those links will now redirect to the main page of Google Adwords instead. However adwords advertisers can still target your websites. This will definitely cause some inconvenience.
Frankly, i think this is a good move. I think this makes the ads look much cleaner now. There will be no more “Advertise Your Site” text with ads



