There are two main ways to look at mass media from a sociological perspective.
First, we can look at it from the structuralist perspective. This perspective says that the media plays a role in keeping our society stable and functioning. The mass media give us common perspectives and common experiences. We watch the same TV shows and the same newscasts. To the extent that this happens, in makes us more connected as a society.
Second, we can look at it from the conflict perspective. From this perspective, the mass media is a tool of the elites that they use to keep the lower classes subjugated. The mass media encourage people not to question the basic inequalities in our society. They do this by keeping us entertained and also by presenting us with information in a way that makes us think our society is perfectly normal and that the inequalities are simply part of life.
I'm not sure what "sociological" means, so I can't give that answer. But in the form of another answer, I'd say that it serves to reinforce attitudes, customs, ideas, of the status quo. I can't even stand watching the news anymore, because I despise the condescencion of the news anchors: "Well, today this is what happened. You should feel a sense of alarm and panic because the sky is falling. We are feeling a little cold today, aren't we? Yes we are. Now, our weather anchor is going to tell us why we feel cold, and what you should expect for the next week every five minutes for the duration of this two hour news program!"
It's also an easy way to get people to buy, buy, buy. I can't think of any media that doesn't encourage this every four to five minutes. The media essentially is like that Batman movie where the riddler (Jim Carrey) hooks everybody's brain to a screen and sucks all their thoughts out of them.