Indeed it's called "top of mind" and it's an old, old marketing tactic with the pinnacle being Kleenex, band-aid, coke, etc.
I get this too. Also get emails where people have uploaded my apps and created an account for me to some korean market.
I think the ones I hate the most though are the emails asking if I want to buy fake ratings.
This has been true on Android also since 4.0
http://www.droid-life.com/2012/10/01/how-to-set-data-limits-on-android-beginners-guide/
Google tends to keep the algorithm secret for apps showing as "top" but I'm pretty sure one of the things they look at is how quickly people uninstall. User retention is (supposedly) a heavily weighted metric.
We gave you an atomic bomb, what do you want, mermaids? -- I. I. Rabi to the Atomic Energy Commission