Do you know why the SIM is cut?
But over time technology developed and then such SIMs could be created which you could put and remove in any mobile but there was no definite format.
But when gradually increasing the use of the SIM card, a problem arose that people were unable to correctly insert the SIM card in the mobile phone and the reason was that the SIM card looked like the same from all sides. Therefore, to get rid of this problem, a corner of SIM was cut so that people could easily identify the correct part of the SIM.
The corner of the SIM, which was cut to bring people out of trouble, has become a unique identification of SIM today. You will get cut in every corner of the world.