The trouble is, if I go to a station for the first time, I don't expect to have to find instructions for how to catch a train from that station. I expect to look at the departure board, identify the platform my train's departing from and whether there are any delays, and assuming there are no delays I'll proceed to that platform. People who don't travel regularly - people heading to the airport, for example - aren't going to look for special instructions for a particular platform as they enter it. As for announcements, there's been plenty of comment on here about the way that the surfeit of announcements leads to people just not listening to them.
It's as if you went to a shop for the first time, got in the wrong queue to pay and were shouted at aggressively by an individual when you got to the front of this queue (and this shouty individual doesn't even look like they are an employee of the shop)