They have the scammers working off phone queues, it takes a little bit of time to get the call to the scammer, who has to start off with a script, so there's a delay.
Remember, the scammer, also likely not a native english speaker, also probably bored out of their mind, has to spin up, they have to read the name, understand how to say it and then say it out loud. Their is a mental startup time that a normal conversation doesn't have.
If someone calls you and isn't ready to immediately respond to "hello" it's a scammer.