a) protests can and will be crushed by the government forces and people will be ultimately defeated;
b) people have no means to force government to enable back freedoms;
c) control is much easier with no internet available.
Russia is on the same path by providing white-list only internet access "during Ukrainian attacks" and a bit longer every time until ultimately internet will become whitelist only.
Also as we have seen specifically in russia, there is no shortage of senior software developers and network engineers truly putting in their best work to block VPNs better and deeper.
Thus Iran's (and russia's) internet blackout may indeed become permanent.
Update: obviously in this comment I am looking at this from the standpoint of an oppressive government.