What is the purpose of having several categories in an item?

I would like to know what is the purpose of Oracle Cloud to have multiple categories assigned to an item, if when generating a purchase request the category cannot be changed?

For example, I have the following article to which I assigned 3 different categories.

But when I generate a requisition line with this same item, the category field is blocked and does not let me choose between the other categories that the item is assigned to.

And this confuses me and I can't understand the role Oracle has in allowing multiple categories to be assigned to the item.

I really appreciate your comments and help.