Interesting fact. I wonder why they could not make it go round in 60 seconds exactly. Did you they have to play with some motor limitations for the seconds hand, or was it purely by design ?
It's to keep all the railway clocks in sync. You could have one that's running up to 1.5s slow and it will still be able to keep up with all the rest, and they're all resynchronised with each other every minute. This is important when it could be the difference between catching a train or not.
To most of us in the world, I am sure, there's a fifteen minute standard deviation on arrival/departure times :(
If it's really that important, why not just use digital clocks?
This was designed in the 50s!
History and culture, it's a symbolic touchstone for the Swiss railway. It could of course be ripped out and replaced with a digital one, but would it be as well loved? Possibly, possibly not.
Because this is a mechanical clock. It has to catch 60 seconds independent of environmental conditions (weather, snow, cold etc.) which adversely affect the performance of the clock.