Why don't people recognize me at all?

Some people even teachers do recognize me some which I had in middle school recognize me , tho some I had in high school didn't which actually surprises me cause high school was like 5 years ago and middle school was probably 9 I'm 22 now anyways I've talked to some of them on fb some say they don't remember me some do and say u look diffrent , ect.. Even with classmates some that I think would remember me don't and some that I haven't seen since middle school do !! Why does this happen
Why don't people recognize me at all?
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