Once upon a time it was considered to be nobody’s business what the state did. Then democracy happened.
Eventually it was decided that it would be democratic for the public to be able to see the data that the state had. The first Freedom of Information Acts (FOIA) were created, allowing the public to request to see the data. This was the first generation.
However, this first attempt turned out to be a bit useless in many cases, because the public did not know the documents existed. How can you ask for something you do not know what is? Of course people could try and cast the net wide and see what came up, or try to gain knowledge of existing documents through alternative routes, but these methods both require dedication, expertise, and time, none of which is very highly available in the world.
In the second generation of Information Acts, it was assumed that the state would create a list of all the data and make it available, online for instance. This is for example what has happened in the European Union (under regulation 1049/2001/EC) and in Norway. This simplified things greatly by making the existence of documents known to people.
But people began to realize quickly that this was annoying. When people knew what data was available, people tended to want to see the actual data. This was fine of course, but caused a lot of work for the people having to deal with the requests. Although a great deal of the data existed in digital format, it wasn’t generally available to people.
So the European Union and Norway amongst others, to simply put most of the documents they had in electronic form on the Internet, and allow people to apply for the rest of the normal process. Some were unavailable because they only existed on paper, while others were unavailable because they were sensitive in some way..
As a result, we now have the third generation of Freedom of Information, in which it was decided to publish all documents online, automatically, with limited exceptions for of privacy, national security, data relating to state regulatory activities, and work documents.
And then there’s just an implicit understanding that it will take several years to bring all the old documents into digital form.