The most obvious reason is that there is no motivation for any of the citizens in a socialistic society to work hard. Few people have the drive to work hard and contribute if there is no reward. With socialism I could be the laziest person in the country and receive the same as the hardest working person. Another bad point is that socialism takes a massive government to redistribute all the wealth. This leads to a lot of waste and corruption that only requires more and more money.
Socialism only benefits the lazy.
I will give Mr. Rothem an example. I had the privilege of working with him on a group project in American Government class. Upon completion of the project each student in the group assigned a grade to the other students in the group. Everyone that worked hard on the project wanted to give the grades fairly according to each person's effort. Those who did not participate as much wanted to get a group agreement that everyone would receive the same good grade.