Like a lot of functions, this one can be used in many different ways to solve many different problems, I think of it as yet another tool in our toolbelts.
So far, the discussion has focused heavily on simply hiding an ID, but that is only one value, why not use it for lots of values! That is what I am doing, I use it to load up the values in a class only one view at a time, because html.beginform creates a new object and if your model object for that view already had some values passed to it, those values will be lost unless you provide a reference to those values in the beginform.
To see a great motivation for the html.hiddenfor, I recommend you see Passing data from a View to a Controller in .NET MVC - "@model" not highlighting