It is necessary, but not sufficient. But you are correct. This is part of why I phrased this in terms of my belief, rather than absolute truth. There's no way to convince me you aren't tracking if it's free. If it is not free, and significantly larger in magnitude than the virtue of tracking, then you at least stand a chance of convincing me.
Grocery stores track you because they can use it to analyze and increase sales, a fairly direct benefit that is difficult to "compete" with as a consumer. Internet companies use it to sell you ads, which is pretty much just about the money, barring exciting conspiracy theories. We can put a decent number on how much money that is, and it really isn't that much money. Facebook makes on the order of $20-40 per year in revenue from a user [1], and the nature of the business is they do better per user than most other people. For something like Cliqz we could easily be "competing" with a revenue of less than $1/year/user, at which point the business case of that extra dollar vs. the catastrophic loss in business if they get caught is a plausible set of incentives I can believe for them to not do it. Not proof, but plausible.
Grocery stores track you because they can use it to analyze and increase sales, a fairly direct benefit that is difficult to "compete" with as a consumer. Internet companies use it to sell you ads, which is pretty much just about the money, barring exciting conspiracy theories. We can put a decent number on how much money that is, and it really isn't that much money. Facebook makes on the order of $20-40 per year in revenue from a user [1], and the nature of the business is they do better per user than most other people. For something like Cliqz we could easily be "competing" with a revenue of less than $1/year/user, at which point the business case of that extra dollar vs. the catastrophic loss in business if they get caught is a plausible set of incentives I can believe for them to not do it. Not proof, but plausible.
[1]: https://news.ycombinator.com/item?id=19462402