I dont know for sure. But I think a part of the problem comes from notation. I dont know how youve approached math education, but I find that students are often times confused by the distinction and overlap between the concept of division and the concept of fractions. I think the cause of this confusion is found in the notation we use and the order in which we teach the subject.
We cant tell them that 10/2 = 5 is division and it requires that the top number be bigger than the bottom number... and explain to them that this is an operation between two integers....
... and then show them something like 2/7 and tell them this isnt an operation between integers, even though it looks like it, but an entire numeric entity all by itself.
My suggestion has always been to restrict ourselves to the use of the obelus when talking about division, and leave the slash or horizontal bar for topics on fractions.
Then after you explain division of fractions, you start showing them the relationship between division of integers and the entity known as a fractions.