If you really don't understand that you're being owned by the scores of ad farms on the net with Google being the largest by far, then nothing I could say would help you understand. I'm sure you know all about web trackers and their ubiquity. But here goes, anyway.
Phone me, at your expense (trackers make you pay for their bandwidth) for a single day, and with each phone call tell me where you are, why you are there, for how long, what you purchased, why you had a medical appointment, the meds you bought and where you purchased them and why, the bordellos you may frequent (not saying you do — it's just an example, so cool your jets), your "special interest" when visiting them, how long you were there, how long you were at the next one followed by your visit to the local courthouse to check the docket under the name Feeder, Bottom and the column listing the charges, six bail-bondsman offices, a dozen car-insurance companies and six body shops, a tire store, a car-stereo store and at last a store selling suits for $49.95.
At that point you discover you have to phone me for every move you make for the next 30 years, which is how long most tracker cookies last before they self-delete, along with Flash tracking super cookies that can't be deleted because Adobe planted them deep in the operating system.
Tell me that's not creepy. But for you, probably not.
P.S. (Requiring an edit)
The ad farms (in this case, me, because of the phone calls) then sell the information to any and all buyers, including health-insurance and car-insurance companies, some police forces or their stooges, department stores and other ad farms, some, like Google, with computer farms the size of continents.
If tracking me and everyone else is worth the billions Google spends on it, it's worth it to me to see that it doesn't.