- Google Chrome for mobile doesn't allow add-ons so you can't install ad-blockers. (You can install browser extensions with Firefox for Android.)
- Google Chrome uses a dark pattern where the address bar tends to send users to the Google search results page instead of to their final destination (compare the behavior with Firefox's). That means that even if you have an ad-blocker, many users are likely to click on Google ads on the way to the destination site, even if they are blocked on the destination site.
- Android doesn't provide fine-grained permissions control or root access, so users can't block ads.
- Some of their content is designed to coerce users to buy restricted Android-based content-consumption devices. For example, you can't buy movies on YouTube and watch them HD in Google Chrome (at least on my computer). You have to buy another computer that doesn't have root access (an Android device) in order to consume the videos in HD. Once you're on the restricted device, it's harder to block ads.
- Google introduces projects like AMP that try to convince webmasters to restrict their monetization options and make it easier to appify the WWW. AMP even serves your content from Google's servers. The more control of the content they have from server-to-eyeball, the more options they have for stopping ad-blockers (and the worse it is for open technology).