In most part of the country, economics talk about capitalism. There are only a few enfaces on socialism. We can say that it’s pretty much depends on the region where the discussion takes place.
But at the same time there is an interest attach to capitalism. And for that reason you are always going to have professors more willing to promote capitalism and almost never socialism. Eventhough by knowing it would have help the students understand capitalism better.
The above statement is back by this logic - you do not know your strength until you know your enemy's weaknesses.
If I live in France I must learn French to communicate. Likewise, if you live in a country that practice mostly capitalism you will be force to learn about capitalism. If you were to lean about socialism your study may not have serve you a great deal in the work place. whatever economic technic you learn from your socialism studies would have been against the economic policies of the corporation you work for.