Every year you hear about one or two people that have died after a ski trip to the Alps. Almost exclusively, they die on/during a night out because they're dressed inappropriately.
As harsh as it may seem, if you go out in a alpine resort at night wearing the same stuff you'd totter around a British city centre in then you deserve the same fate. It's sheer stupidity of the highest level to do anything other than dress for your surroundings. [Nb, OP, this isn't aimed at you, but at people at large]
Yes, the resort's paths and roads will be looked after so won't be hugely icey, yes the clubs and bars will be heated and very warm, yes you most likely won't have far to walk.... But you will have to walk. You will be outside. The temperature at night will be low [-15C would be a 'warm evening' for some resorts].
Noone cares whats on your feet. Frankly, after a day of ski boots then some trainers/vans/converse/whatever your fancy will be a blessed relief and you won't want to part from them. As for clothing... you can get away with all sorts if you wear a coat for protection. Do not rely on a 'beer jacket'.
Some people will say that's all way too OTT and that yes you can go out wearing normal stuff... And sure, you could get away with it. But I wouldn't try.