The situation is quite different in Iran. Traditionally the government had control over all media. Ministry of Culture and Islamic Guidance reviews all books before publishing and may remove the parts it doesn't like or prevent books from being published altogether. Same for newspapers and magazines, except they don't review them before publishing, but if they find something offensive they close the newspaper. The only entity allowed to operate TV or radio channels is Islamic Republic of Iran Broadcasting(IRIB) which is part of the government, etc.
When internet became popular, the government monopoly got threatened. Since then they did everything in their power to restrict the use of internet. First they passed regulations that forced private ISPs to buy their bandwidth through a government organization and deployed a censorship software (rumored to be Chinese) on all of it, so blocking is national not per ISP. The they passed a law restricting home users to 128 kbps (yes, kilobits per second not even kilobytes). Then they criminalized providing anti-censorship solutions (but not using them, although it is debated). In some occasions (like after 2009 election), they make the internet so slow it is virtually impossible to use. HTTPS traffic is always slower than HTTP and occasionally completely blocked.
It is all about maintaining power to control the narrative. As I said, it hasn't worked as well as they have expected. Now they are building something called National Internet. They say they don't plan to block access to the internet but I am not so hopeful.
It has been a decade-long battle between government and freedom of information and speech. Most people who are affected aren't dissidents, but simply people who want to update their Facebook status.
It is sad because we are a fairly developed country. There is no war or famine, our healthcare system is good, we have powerful industries, good universities, big cities with good public transportation and interstate highways, etc.
The problem is that over the years since the Islamic Revolution our nation has become more liberal in general while the government remains rigidly conservative. It will be a long answer to describe where we are and how we got here, but I think this short comment is enough to answer your question.