The shortest reason is the very simple fact that there is no utopia.
But the slightly longer reason is that the core assumption of central planning is that someone else somewhere else who doesn't know you can make your life better. This is simply not possible.
Why not? Consider the number of economic decisions you make per week. What type and volume of food and from where, for example. For a single man this involves many factors, such as his own skill in cooking, the amount of time for food preparation, and many more. For a mother these decisions must consider everything from her food budget to the distance to the various stores to the volume of storage to the food preferences of her children. There is simply no way even a local 'expert' can be as efficient as either of these two people have the potential to be.
The the total economic activity of just one family is much more complex and each additional family adds to this complexity. The sheer volume of data needed to perform such planning is daunting and will always result in 'central planning' devolving into limiting choices and options. This can also be called 'making it harder for families to do what they need' or, more bluntly, 'limiting moral agency for the sake of convenience'.
This is why Edan rejects the traditional view of Socialism; it is obviously impractical. Instead the goal of Edan is to recognize the legitimate role of government: protecting the family.