Now this is a new one on me. I take all sorts of stuff to exhibitions but have never considered a clothes rail.
This one was seen in the centre of the Gauge 1 layout "Stanley Midland". At first it seems an odd addition to the kit but on reflection, there will be a quite a crew as they only tend to bring a couple of locos each, and they will probably all have coats. The resulting pile would be quite a mound in the middle of the layout. Anyway, G1 modellers tend to be dapper chaps and so they won't want their tweeds on the floor.
Worse, they could actually be a fire hazard - coal fired locos can chuck out sparks from the chimney so loads of cloth lying around probably isn't a good idea.
The crucial thing though is that your model engineer likes to wear a workshop overall (think a laboratory coat but in brown, like the sort of thing Arthur English wore in "Are you being served") when operating his locomotive and this is incompatible with an overcoat. Hence, coats are replaced with more suitable apparel during the operating session.
This has me thinking - maybe a stylish chap should carry all the railway kit, and clothes, in a gentleman's travelling trunk !