It's an established strategy to serve you irrelevant ads. When the targeting gets too specific, the people start to notice and panic.
Target is a fun example - they had cases where they revealed pregnancies through targeted ads. Now, they'll put an ad of a lawnmower (untargeted) next to the bassinet (targeted) and customers are less creeped out
Idk of it is a strategy, would be interested for any background reading.
My XP at an ad-tech is that there is only so many targeted ads, and the advertisers cap how many times they want to show you an ad. When it comes time to bid to show you an ad, all of the targeted ads might have exhausted their campaigns (shown you the ad X times already, or the campaign ran out of spend). In this case, all the advertisers that would bid a _lot_ in auction are sitting out. There are still other bidders, but these are less targeted and are bidding less money. Because the highly targetted ads are exhausted, these lower targeted ads might look random. Their targeting might be instead of based on gender, city, income, the targeting might be based on just geography. The fewer targeting parameters, the lower the bid.
In effect, once all the highpy targeted campaigns are done with you, they stop bidding, and the ads with less targeting which have cheaper bids are now the auction winners. If those are exhausted too, then there is a very large pool of low rent ads which have even less targetting.
Here's a skeptical write-up about the mailers I was referencing. I like this view because it acknowledges human fallacies. For example, that an untargeted ad could feel targeted or that we may exaggerate the amount of ads that feel targeted.
Target is a fun example - they had cases where they revealed pregnancies through targeted ads. Now, they'll put an ad of a lawnmower (untargeted) next to the bassinet (targeted) and customers are less creeped out