Jon, no one will try to make you tip anyone anything. If you don't want to tip, then by all means don't.
The first time I cruised where they used this system I thought I wouldn't like it but now I'm convinced it's the best way. Just my opinion.
As far as the cruise line adding the tips on up front, that is for the convience of both passengers and staff at the front desk. Can you Imagine waiting til the last night to add tips on 2500 passengers accounts and the resulting nightmare it would create with hundreds trying to adjust them up or down all at the last minute?
All you need to do is sometime during the week go by the pursers desk and ask for the form to adjust the tips. It's quick, painless and not a big deal.
Go and enjoy your cruise and don't sweat the small stuff.