Some companies seem to have the idea that humour equates to great customer service. (e.g. WestJet and Amtrak)
There's nothing wrong with lightening things up and getting people smiling, but you also need to fix the underlying system. Telling someone a joke while they are on hold for an hour doesn't change the fact that they were on hold for a hour.
And not everyone makes a good comedian. Management can dictate "you shall tell jokes" but that doesn't mean it's always going to be funny. Especially the fifth time you hear it.
Unless you also fix the real issues you're just putting lipstick on a pig.
Of course, that leaves the question - if you can't fix the pig are you better off at least dressing it up?
If this was individuals trying to make the best of a situation then ok. But in most cases it seems to be a top down directive. In other words it's coming from exactly the people that could actually fix the system if they really wanted to.