Automatic grats - What they aren't telling you

I've gone back and forth on this subject more times than I can count now and I'm still not sure where I fall on the subject. On the one hand I tend to think how dare someone tell me I have to tip; on the other hand I also know how hard the crew work and how much they rely on those tips to make up their wages.
However I found out something today that several large cruise lines all do that really shocked me.

Gratuities - I think I've changed my mind

Anyone who has read my blogs before will know that I’ve always been pretty against tipping when it’s been made compulsory. It’s not that I’m tight, (honestly), I just begrudge having to pre pay for a service that I haven’t received yet.

It’s also always irritated me that society only deems certain occupations as ‘tip worthy’.
Why should I tip my taxi driver but not my bus driver?
Why tip my waiter in a nice restaurant but not the serving staff of McDonalds?