My guess is targeted advertising works great up until the point you share your devices with other people. parents and their kids sharing accounts, laptops, tablets leads to a bunch of junk input and this makes up the majority of population
Personal anecdote but my personal experience is that targeted advertising seems to be predicting my past me. I can't describe it exactly, but it seems to never realise that I'm done with (something), especially with once-in-a-moon purchases (like laptops).
