Amazon also doesn't know if this is a single use or consumable item. Some things have significant marginal utility beyond 1, and others can be consumed and need to be reordered. (Charging cables, Amazon echo for multiple rooms, paper goods, etc.)
How often do I buy a HP Color LaserJet printer, versus toner cartridges for it? Or ink for another printer of which it has no evidence that I own)?
Yet I bought a color laser printer and my first two pages of recommendations are for other variations on the same ("Hey, you bought the wired MFP! Perhaps you want the wireless too! And I know it's a HP printer, but maybe I can suggest some Brother toner for you!").
You're correct that Amazon should be smarter about some recommendations. I'd say give them the benefit of the doubt in that they may have found an algorithm that works most of the time (or at least when it comes to their bottom line), but edge-cases stand out to us.
Still though, there could be a method to the madness. You bought a printer - are you setting up a home office? Perhaps you want a second printer for upstairs?
Also, you just bought an HP brand printer. Were you replacing a printer that just ran out of ink? Maybe THAT printer was a Brother printer. Perhaps this Brother ink cartridge can extend the life of the hypothetical printer you may be replacing...
My point is that I can contrive cases where the recommendations might make sense - not to you, specifically, but to a large enough cross-section of consumers.
I don’t doubt there are entire divisions in Amazon that draw statistical correlations and do A/B testing to figure out what annoying emails work. Just like any other marketing agency. So you can be sure that any annoying email you get is the probably the result of years of metrics.
