[jahewson]

That’s most likely because your device used their wifi and ended up behind their nat using the same ip as them. The anonymous tracking cookie ids on your device get associated with searches from that ip. (i.e. “cookie 1234 is in-market for glazing”) and you take those cookies back home with you. This is actually a massive failure because you’re not likely to purchase glazing at all.

[Nextgrid]

I'm not sure it's a failure. You could argue that showing him ads for glazing could be beneficial in case he spots a good deal and decides to talk to them about it.

Now I don't think the ad network is that smart and explicitly intended for this, but presumably in aggregate they're seeing better results by merging targeting buckets by IP than not, so they continue doing it.