For one, there is limited space. There are also no refrigeration facilities. Currently shuttles are stocked with enough food to last the full length of the mission, plus extra should they encounter any emergencies. This is fine for short missions but it becomes more of an issue when the shuttle will be in orbit long term.

The challenge for SMRC is to produce a prototype that can “synthesise” healthy and tasty food that will beat the dehydrated meals currently eaten by the astronauts. The plan is to use a combination of 3d printing, which will provide macronutrients (carbohydrates, protein and fat needed for calories or energy) and inkjet printing, which will provide the flavour, smell and micronutrients (vitamins and minerals).
In order to make sure the food actually tastes and smells of what it is supposed to be, SMRC are also working along with the food science program at North Carolina State University. Who knows maybe it will receive a Michelin Star!
If this works, then there will be no need to take along full pre-packed meals. Instead they will be able to take just generic or basic ingredients which can then be printed into a meal.