I wonder governments shouldn't have the duty to regroup all those website and host them somewhere? Something like archives.org for governemental websites.

I think governments can, and will, argue that this kind of maintenance is outside of their budget and abilities. Given debacles like the Healthcare.gov website, they're continuing to make a strong case for that.

You have a point. Nonetheless, this kind of information should be thought as the same thing as books in library, and governments do have the budget for libraries. It could very well be a matter of time and perspective.