For me there's too many confused punters out there already, getting on the wrong train, pressing the wrong button in the loo, not being able to find the handle (loo or carriage door) to start introducing extra things. There are dozens of Saint locations on the railways, from St Pancras to St Keyne, and a few of them are even duplicated like St Margarets, so whether it's St Paddy's day or not it's a chance of confusion too much, it's far too much like a possibly real station name. Many people simply wouldn't ask around for confirmation from staff or other passengers. They've got their itinerary printed off and they'd see the train wasn't advertised on displays to the station their train was going to, and so would simply avoid it. "So what if you miss your train you've booked your advance on and have to pay through the nose for a new ticket, it's a joke for one day only!"
In a not too dissimilar fashion, wasn't it not long ago that passengers started passing their stations due to the contractor's name being displayed during works and the passengers were mistaking it for their station name? Not all were unfamiliar with the station they were going to either, and certainly not all, if any, were foreign visitors, but for long enough to miss their stop, just once, they thought there was (I think) a Huntington station.