You wouldn't get much sympathy from customers, the general public and media if the driver was seen to be hiding away at the back of a train because of the risk of collision to which everyone else onboard would be more exposed. Having a responsible staff member at the front of the train making key decisions even if not adjusting the controls very much between stations in this era of ATO is a big part of the psychology of safety, and there are things a set of eyeballs directly connected to a well-trained sentient brain can sometimes notice that machine systems and even the very best live video feeds to a remote operator would be hard pressed to catch, precisely because they're not very well defined: Early warning of livestock incursion or a tree that didn't actually cause a problem for the train concerned but might be leaning in a little closer than usual/comfortable for example; a group of youths messing about on a bridge; someone looking troubled at the lonely end of a fast line platform where no train is due to stop for ages, etc.