That's entirely pragmatic in this data collecting age. Being silent and hanging up as soon as you hear the spam won't get you marked as a phone line that has a human on the other end nor do you risk your voice being recorded. If you're silly enough to say your name when answering you'll just end up with text and email that is now personalised with your name (it's much faster to identify and hang up when their best intro is to say "hello who am i speaking to?" on a single person line click).
I don't know anyone in my age bracket (45) who doesn't do this let alone those younger. It's entirely understood and expected. Fuck anyone who says it's rude and those of an age particularly prone to falling for scams (70+ and 15under) should be encouraged to do this. You should be telling your kids "never say anything on picking up, let the caller to your phone identify themselves! They could be scammers trying to get your details such as your name".
I feel all these "OMG the kids don't say hello anymore they have no etiquette!!!" statements are either from the clueless or from spammers frustrated that it's much harder to get through if you don't know their name.