After our first cruise, DW and I did a revenue/cost analysis of where the ship would have been financially if everyone cruised the same as we do [i.e. non-drinking, non-gambling, but some on-board shopping]. We concluded that the basic service charge is not really a "tip" at all, but another part of the cruise cost, like taxes, that is separated from the fare, probably so they can show TA's a higher commission percentage while keeping the actual amount down.
Accordingly, we just consider it part of the fare when comparing and selecting a cruise. While it is true that service may not always be up to standards, consider that these people have to live on the ship and they can't fish a replacement out of the sea. If someone is sick, they have to go with a short team or risk spreading the sickness.
I highly recommend "Cruise Confidential" by Brian David Bruns. It helped me to see myself as others see me.