Value is in the eye of the beholder. Princess has enough data to know that 75%+ of passengers buy a package and that many do it as suggested by most on here for the convenience of not having to worry about an end of cruise bill being unexpectedly higher than planned. It makes sense for the cruise line to offer it, and it makes sense for the consumer to buy it if it fits their lifestyle.
We don't buy the package because when I do the math for us, it would cost us more than double the cost of wifi and tips to have it for what value it provides. Lucky or unlucky, we cut out things like sugary drinks a couple of years ago, and so basically we bring onboard what we want to drink outside of what is included, and it works perfectly well for us. If most people buying the packages keeps the cruise fare from going up as quickly, then it's a win for everyone along the way.
Packages also allow the cruise line to lock in tips and wifi for those who might not normally include those items or use them. Again, a win/win.