Should kids cruise free?

I've been working as a travel agent for awhile now and I've lost track of the times someone has said to me
"I'm not paying for my child, he's only two", or, "I'm not paying gratuities for my 10 month old, why should I?"
As a Father myself of a three year old boy and a one year old girl I would never dream of expecting this on a cruise. and I'll tell you why.