>Candidates who meet individual voters on market squares and public places obviously try to find out which of the voter's wires are hot and try to deliberately connect on those levels that are meaningful to the potential voter.

That's becuase, in terms of consent, you're consenting to such actions by going out to the public square. You're not knowingly consenting to your life's history being sold and traded on a black market that's then used to target you for such speeches when browsing on the internet.

For your analogy to be comparative to what's going on, you should, instead, think of it in terms of a politician showing up to solely your house because you're the sole democrat in a republican city in, say, Texas. (This demonstration based on the fact that this is an American board.) This could be easily inferred from your social media, browsing history, metadata collected by the government, etc.