Well... quite a lot of jobsworths' in this thread!
I've never had him, but I've had friends who frequent the Southern network who have had him a few times - they really appreciate it. It's a small thing that the passengers legitimately enjoy, and Southern are probably just happy to have anything that makes their customers less angry at this point.
I'd expect the driver to have good judgement and use the PA in this way as long as it isn't interfering with their other duties and not putting his passengers in any undue danger. In fact, as they're more likely to listen to him, I'd say this is a good thing. Steve (and other unicorns like him) are a rare breed and they wouldn't be getting recognised for awards if their behaviour was putting passengerts into harms' way.