Princess is getting a lot of dependable revenue with the plus packages and not paying out a lot for the products. They know that they will be getting $60/day everyday from that person. Where as, since we get the standard package, they don't know if we will drink or not that day (maybe we don't feel well that day). They don't know if we will purchase the Internet plan, etc. They can't anticipate our spending.
They push the Plus & Premium packages, because it's cash in hand with little expense to them.
Most people have no more than 5 or 6 drinks/day. Each drink probably costs them $1-$3.
Now, they will offer the free casual dining venues to entice people to eat there. People love stuff for "free" so Princess is hoping that people will opt to eat a cheaper to prepare meal ( ie pasta, sandwich, etc) instead of going to the MDR and having a full meal. In addition, it will also lighten the load that the busy MDR usually experiences while the casual dining options are like ghost towns.
And BTW... you do realize that when you purchase the plus package $120 ($60x2) and also get the princess insurance, that you are paying the 8% insurance premium on that additional amount for a total of almost $130/day.