Information can be used as a weapon. Government wants to control weapons and forbid it sometimes. I think that's an obvious answer.
Are you really surprised that most of them comply? What other choice do they have?
Definition weapon - a thing designed or used for inflicting bodily harm or physical damage.
But certainly information can be used for extortion, or to otherwise coerce people against their will, and maybe that's enough?
"Information" is a noun, hence it is a "thing".
Furthermore, the 'physical damage' it can inflict is the destruction or manipulation of physical memory cell states.
By itself, it is harmless, but when paired with an appropriate device, by a user with malicious intent, it can then be used to cause harm.