I accidentally called one back a few days ago and incoming robocalls have gone through the roof. I have no proof that that's why, but I won't rule it out.
On a more positive note, Hiya has been working really well identifying spam/robocalls, so I don't actually pick them up.
Anecdotally, I've noticed a decrease since a few months ago (my call blocker log shows 1 call in all of January) and I've been picking up, striking up a conversation for 10-15 seconds then continuing the same with hardcore insults in a relaxed, deadpan manner, as if we were still discussing their IT assistance/credit card "refund"/cruise/security system offer. If they start yelling I just hang up. Some people try to keep selling me their crap, that is funny; I've got quite a few stunned silences punctuated by huffs and puffs, and I made one scammer sob, that was great (I guess whatever I told him about his call center job was accidentally well targeted); so it's also great entertainment and takes very little time, you can have them on speakerphone and keep working/reading/working out/etc.
I like to think they put me on an actual do not call list since I tie up and annoy their operators for as long as possible. One time getting the same guy a dozen times before he finally gave up and from what I can guess just went on a long lunch lol.
That doesn't sound like a worthwhile use of time though. What would be cool is if we could transfer the call to a robo responder and have it be smart enough to act like a really dumb person.
It should also learn the caller's speech and slowly overtime change it's own voice to sound more and more like the caller. Eventually the caller would be talking to themself... same accent, cadence, vocabulary, etc. LOL