When you analyze a page with the Page Speed tool, it will display suggestions that you can use to make your page faster. The difference is that now you can use the "Analyze" menu to determine if a suggestion is related to your own content our to ads and trackers.
Google recently made it a point to stat including page speed as a signal in its search ranking algorithm. The main motivation for this was that it is simply better for the user experience.
As you probably know, ads can slow down a site. While clearly users may find ads annoying at times, slow-loading ads are going to do nothing to make them less annoying, which is why this tool can also enhance the user experience.
If you ever listen to what Google has to say about ranking, you're most likely going to hear something about improving the quality of your site, and offering a better user experience. While Google has over 200 signals for determining rank, you can bet that most of them are related to this simple concept.
You should also consider that ranking in Google is not the only way people can get to your site. Social sites, review sites, etc. may be playing increasingly important roles in driving traffic to your site these days. No matter how they get there, they're likely to leave if your site is hanging up because of ads.