Why do girls come up a measure themselves next to me? I'm not even that hot?

Im 6’3” and all these girls in my class seem to be making this big deal about how tall I am, even my teacher lol. They’ll like skip over to me all giggly like “let me compare myself to him” usually they are always around the shoulder mark (people just need to grow lol), and they all ask me for piggy backs and to carry them lol. Im not insecure about my height at all, I actually love being tall, but the whole “wow your tall” “your nice and tall” and all everything to do with tall gets a little annoying, I see it as a compliment and enjoy the attention but you know when a pretty girl gets told how beautiful they are 24/7 it does get annoying after a while even though it’s a compliment you know, same thing as that. So what do you think there deal is? One time they were all like grabbing up my arms while we were walking trying to link arms with me lol, another girl literally grabbed my arm put it around her and held it there will we was walking lol (odd). I know it’s bad to say but I honestly don’t think im that special looks wise, I think I can pass for cute but no-ones going to say im H.O.T or smoking or anything which is why all this attention is a little I dunno odd lol, I mean if I was up myself and fought “dang im hot” I’d consider it as “normal” I guess but I don’t lol. Why do you think they all do this, like every girl in my class Im 17 btw.