If children attend a school where everybody celebrates Christmas and everybody expects Father Christmas to visit, they see the Elf on the Shelf as an extension to the Father Christmas thing that some children are getting and they are not.
But there are a million variations on what Santa does or doesn't deliver
Sometimes Santa brings the stocking, sometimes the main presents, there is often huge variation in the type of presents he delivers
Some see Santa in Winter Wonderland type stuff before christmas, others don't
Some go to lapland, most don't
Some get advent calendars, others don't
Eventually, someone will pop up in your class who isn't visited by Santa, and that's something you'll have to deal with.
I just don't get this narrative that we cope with all of these other variations on experiences of Santa, but the Elf creates difficulties on another level. It sounds like post rationalizing of a generalised dislike (which is what I suspect it is).
In the past, I have quietly told upset children that the elf on the shelf doesn't visit them because Father Christmas knows how amazingly well-behaved they are so hasn't had to send an elf to their house to keep an eye on them. Really cheers them up and it has never yet got back to those who have visits from the elf!
For obvious reasons, I don't think this is a particularly stellar way of dealing with the situation. However, I suspect my own DS would happily trade not being 'amazingly well-behaved' for the fun of the elf and I'm sure that's true of many.