Maybe. The current heuristic is "he has bought X so show him an ad for X", but would it be so difficult to flip that to "he has bought X so show him the next thing on the list of interests we know he has" or even just "anything but X". I strongly suspect noone is doing this because there is no point, they get paid the same regardless.
That's not the current heuristic; it's not nearly that simple.
Think about how you know if someone is interested in something. What does it mean to be interested? How does that translate into a sale?
A person just bought a vacuum cleaner. Does that mean they are interested in vacuum cleaners? Are vacuum cleaners things that people get interested in? Do people who are interested in vacuum cleaners buy more than people who are not interested in vacuum cleaners?
To us these answers are so obvious that it's humorous. To a computer, not so much.
There are many millions of interests, opinions, and things to buy--so count the combinations. We understand it all intuitively because we are adult humans with decades of experience in this society.
This is why search and ad companies hire so many AI researchers.
EDIT: to understand the financial incentives, see my other reply to you. In a PPC ecosystem it is better to match too greedily than to risk missing a customer ready to buy.
