Don't forget the IFE - that can suck up a lot of juice.
I suppose you could theoretically reduce the size of the generators but on a twin, just one of them needs to be able to run all essential services in the case of engine and/or generator failure. You don't want to load-shed the FBW to get the anti-icing to work.
I'm not an aircraft systems engineer but even I can see that it's better to over-specify the electrical power sources as you don't know what might be fitted to the airframe in the future. Passengers won't be impressed by the lights going out every time someone flushes the toilet!