It is obvious that social medias have revolutionized our way of life and change our behaviour. One of the main reasons of their success is their facility of use and their practicality and I think that's why lots of  people get their news on social media and no more on newspaper or TV.

First, social media allows you to get information everywhere and everytime for free.  You have no more to go out to buy the newspapers to obtain the news. This accessibility is also allowed by the TV but you have more different sources and point of views on social media than on TV. Moreover, social medias are the only platform that allows people to share their opinions on a subject online and with other people. Indeed, people tends to be more and more suspicious to traditional supports of information that generally share the same views and belongs to the same companies and people that adopt political correctness. I think that social media answer to this need of people who want to make their own opinion and don't want to follow the views broadcast by the mainstream media.
In addition, social networks have algorithms that know the subject that interested you and present them to you. You haven't to search the news that are important for you because the task is already doing by the social media.  You earn lot of time by getting only the information that matters to you.
Then you can easily go back to the information that interested you and the news don't take place in your home contrary to a newspaper.
In a nutshell, more people get their news on social media because it's free, easy to access, you can have a wide range of sources and point of views and you can react to the news.