Re: I want to discriminated correctly!
"They are stereotypical because it works"
No, they are stereotypical because people selling advertising sell advertising. That's all they do. They really have no idea about who's reading their crap but they're safe in the knowledge that the advertisers are no better informed so they can keep selling their "insights" to their marks.
Take the situation here. SWMBO does some searches then says "If you're on Amazon can you order $PRESENTS_FOR_GRANDDAUGHTER". Consequently Amazon now offers, based on my previous purchases, stuff suitable for a 15-yo girl. I'd seriously believe they know what they're doing if in about 11 months' time they start showing stuff suitable for a 16-yo girl. It would, by their standards, be an improvement if searching for "desoldering" didn't bring up mostly soldering irons with a few heated solder pots thrown in for good measure. By contrast I'm due to receive the latest order of stuff I previously ordered months ago; I had to search back orders to find it.