Because it was very human oriented and an average man felt safer because he had basic needs (job, food, home, holidays, career) delivered on plate rather than today where he needs to compete for somewhat trivial needs. With 40-80's technology that was of course irrational and had to force such country in debt in long term. In my opinion there was morally nothing wrong with such system, one could even say it was really good hearted…but it was also not realistic. Maybe in future with rapid technology advance some aspects of such economy will be viable (Start Trek as some futuristic socialist civilization comes to mind).