@f I suspect, like most things these days (ads, spam, etc.), it's a numbers game. If they can weed out the people who ultimately won't fall for the scam, they can save money wasted on efforts that won't return on investment.
Plus, wasting scammers time has become a form of entertainment. People are making money on YouTube (and some companies are selling services that will waste your scammers' time too). So getting off the call sooner rather than later improves their return on investment.