Cop. 1, Copy 2

My mother pointed this out the other day when I checked out a DVD from the library:

"Cop." is the same number of characters as "Copy".
So why bother to abbreviate it? Look at the little white label. I don't think it's a matter of space, is it? I realize that the "y" takes up a little more room than the "." but not so much that it's a make it or break it kind of character.
Amusing, really. I never noticed when I worked at library for several years of my life. I'll have to ask my library friends for insight.