I think it might seem odd because it wasn't something that was done when we/I was a child (sorry OP if you're younger than me
) and the advent calendars then were mostly just pictures behind a door.
I can remember one year getting one with little plastic toys in it and then after that the chocolate ones seemed to take over, but through my early childhood it was always picture ones only.
We were very close to my grandparents on both sides, lived across the road from my Dad's parents and saw them every day, and close enough to my Mum's that we could easily visit two or three times a week, and they were very generous, but it would have been unusual for us to get an advent calendar from them or any other relatives. And certainly not from the neighbours.
And it wasn't the norm for my friends to get more than one advent calendar either. I remember, because we used to compare pictures when we got to school. If you got a candle as the picture it was always disappointing, but a snowman or a robin was always good. Part of the excitement was guessing what picture you might get before you opened the door.
By the time my brother had kids it seemed a bit more of a thing for other people to buy them advent calendars as well (they are 16 and 19 now so born in mid/late 90's) and now I've had DS (age 5) other people do get him a calendar sometimes. My parents keep the one they buy at their house though, as he visits them regularly and so can open it with them.
So I can see what you mean OP, to me it's a more recent thing, it's not something that was really done when I was a child and so it can seem a bit odd or excessive for one child to have several advent calendars.