As parents and caretakers of children, one of the difficult lessons to teach our kids is the concept of sharing. On the flip side, it is important to also teach children to return things they have borrowed from others.
Books teach children to share and the bookplates teach kids that when a book does not belong to them it needs to be returned to its rightful owner.
Of course, another way to teach children about the sharing and borrowing of books is by taking them to the local library. Libraries share their books with us but also insist they must be returned in a timely manner.
For me, it has been far too long since I took a child to a library. It would have been with my son when he was young.