I think I have an idea of why, though I haven't been able to articulate it properly yet.
I've been thinking about it a lot recently because I co-work with a bunch of digital marketers, and some of them have affiliate marketing sites with domains that follow the pattern http://yourexactsearchterm.com.
The best I can come up with is the Uncanny Valley of SEO, where it feels like a website was made and over-optimized specifically for people making my exact search query. Maybe this is unfair or confirmation bias, but I feel like those websites are the most likely to be low quality content farms (e.g. paying content writers pennies to regurgitate content they have no experience with and/or don't understand). Either that, or they are outright scams.
Do any digital marketers here have opinions about this?