Some trackers are very good and useful. We use Google Analytics to help figure out what pages people like and whether certain browsers cause issues and things like that. You can of course block it with a plugin if you can't stand the idea of that, it just means we'll have less insight into how to improve your experience.
The ad trackers are not controlled by us directly. We use 3rd party advertisers which are fairly standard. Much of the time they don't need trackers because they are "direct sale" ads, but some of the time they still use trackers.