I was in senior high school in China there were only 4 classmates out of 35-ish including me don't wear glasses. This was like 2007, before the smartphone took

I was in senior high school in China there were only 4 classmates out of 35-ish including me don't wear glasses. This was like 2007, before the smartphone took off in China. I have no idea how come did this happen but one of my assumptions is the ruthless study plan for young kids.