Cal Newport, in his book Digital Minimalisn, explains that there are two forces that encourage behavioural addiction when using social networks.
The first force, intermittent positive reinforcement, exploits the fact that rewards delivered unpredictably are more enticing than those delivered with a known pattern. The expectation of likes/hearts/retweets after posting online is comparable to gambling.
The second force is the the drive for social approval. Social media is tuned to offer us a rich stream of information about how much (or how little) our friends are thinking about us at the moment.
We didn’t sign up for the digital lives we now lead. They were instead, to a large extent, crafted in boardrooms to serve the interests of a select group of technology investors. – Cal Newport, Digital Minimalism
A quick test to see how deep these two forces have taken hold of your behavior: delete your Facebook and Instagram apps from your phone for just one day, and see if you show signs of abstinence syndrome. You can always reinstall the apps later if you want.