I think the shrink wrapping of luggage is a waste of money to be honest. It doesn't give you any extra security merely demonstrates to you immediately on sight that the luggage has been tampered with!
And that is the whole point of it! It enables you to tell whether your luggage has been tampered with and to take action immediately before you leave the airport rather than discovering this only once you've got home. Havana airport was always notorious for thefts from baggage and now Cubana won't check-in baggage that hasn't been shrinkwrapped first - they provide the service free precisely because at every stage of the check-in and baggage handling process it enables all staff and security in particular to tell whether a case has been tampered with. It's cut down their pilferage problems and complaints as a result.
I do think though that it can be a potential deterrent in other circumstances too. Why go to the bother of cutting through shrinkwrap, which can in my experience actually be a bit of fiddle to remove, when there will be plenty of cases that will be easier to get into and which won't draw attention to you when you end up surrounded by or trying to dispose of all that clingfilm?
SM