The number of potential reasons is loco, fell down a short rabbit hole, but then my eyes started to glaze over. The variability of dates that various countries apply DST is much too loco.My Dad had a theory on what you are talking about. He believed that a big factor in other countries aping our DST clock stuff was mainly due to the opening and closing bell of the New York Stock Exchange. That being the one daily event important people around the world pay the most attention to.
Mexico saw the light in '22. Would be great if the rest of NA would see the light.