[LunaTheHamster1]

Yes they are necessary, without them so many hamsters would be worse off. Personally, i think the absolute minimum should be 80x50cm, but I use approx 100x50cm for any species, unless for medical reasons or older hamster or one that doesn't like a big cage ( always an exception to a rule of thumb).
I actually think they need more space, but you have to be realistic and without animal organisations and pet stores being on board it's never going to happen.
When I have a home big enough i hope to make my hamsters cages even bigger, if they like it.