If I'm in the market for something, I'm likely to indicate that by doing a search for relevant terms. So the search engine could sell associated ad space to appropriate categories of advertizers.

If I'm reading reviews about a certain product category, it's a fair bet I might be in the market for such a product. So the site could show me relevant ads.

If I'm reading a site devoted to a particular topic or activity, the publisher might reasonably guess that I could be in the market for related products, and offer relevant ads.

None of this requires any privacy-invasive tracking.

If I'm reading a general news site, the site shouldn't have any more idea what I'm "in the market for" than the publisher of a print newspaper I might buy.

If I'm browsing used-car listings, the site shouldn't have any idea what genre of novels I like to read, what my grocery cart usually contains, where I go to work out, or how many pets I have. Why does anyone think it's OK for a company to surreptitiously gather that sort of personal information about everyone?