One thing that Amazon does is shove a load of adverts, i.e. leaflets, into their parcels. Given that Google is also a behemoth in the ad industry, this might just make sense.
I've been a Prime member for 3-5 years, I guess, and we've gotten dozens and dozens of them through the years. I can say that I cannot actually remember the last time I received one. I can, however, remember that it was a "Cell phones for servicemen" or something like that.
My most recent order from Amazon UK had three leaflets: a voucher for Naked Wines, a voucher for Ocada and something else that I can't remember. Most orders I get from Amazon have at least one leaflet, it's the same for other online retailers, such as Play.com.