Why do all passports look almost the same?

At one conference in October 1920 in France, the way we travel is forever changed. Then a modern passport was created.
The passports of all countries look similar: They have a similar number of pages, size and design.
This is because the League of Nations, an organization for the preservation of the world peace established after the First World War, established a framework of rules for printing passports during the Paris Conference. Then, for the first time, a set of standards for all member states was established.
Prior to the First World War, passports were not needed for traveling across Europe, and crossing the border was very simple. However, everything changed in the war.
European governments had to limit immigration and travel for safety reasons, and checks were stricter.
After the war, the maintenance of fragile security was a priority, but the lack of standardized traveler data documents made it much more difficult for the border guards.
Everything and when people had all the documents with them, there could be a suspicion of their authenticity.
The Paris Conference on Passports and Customs formalities and travel cards prescribed the dimensions and design of travel documents for the 42 member countries of the League of Nations.
At that time, the passport had to have dimensions of 15.5cm x 10.5cm, 32 pages, of which the first four would include a description of the owner's appearance and personal data, while the other 28 would have recorded visas to enter those countries where the passport was valid .
All passports had to have a cardboard tie, and on the front cover the name and the coat of arms of the state.
Although the standards are now under the auspices of the United Nations International Civil Aviation Organization, the design of the passport is virtually unchanged for nearly 100 years.
The most important changes in the standards were the introduction of a watermark, and then the installation of chips with biometric data.