Ever watch a commercial and think “I would NEVER buy that product” or “what kind of people watch this show? Why would I want to use/buy xyz?”
To focus online ads, many advertising companies track your activity as you browse from website to website (where their ads are displayed) and will build a profile of you to present more useful ads according to your interests and assumed demographics. These companies don’t collect personal information like your name and address; thus, you may find this information gathering helpful as you find yourself being offered more customized advertisements.
Or, you may see it as a violation of your privacy.
Simply disabling cookies will not alter the fact that your public IP address is available to these companies and, if you’re the only person/family using that address, you’ll still be profiled. If you’d like to opt out of these types of ads, you can do so very easily.