Reasons for discontinuing social media vary: it eats up time, it results in conflict, people make catty remarks, and it fosters a sense of discontent and dissatisfaction with one's own life and accomplishments. A big one, in my opinion, is the time it demands to follow others and to write about oneself.
There's the realization that web pages are a form of self-advertisement. Some people find it needful to portray their life as more interesting and successful that it really is, given that so many others engage in glowing self-descriptions.
Lately, though, another reason has emerged from the chorus of people angry at the doings of Donald Trump. While you might expect conflict and irritation by people who disapprove of his particular viewpoint, and sometimes this gets rebutted impolitely, some people expressed dissatisfaction with being exposed to people incessantly complaining about politics; even if they largely agreed with the viewpoints being expressed.
I think this is the result of the repeated reminders that things are off kilter; and that things are as bad as they seem. There's no respite from reality. Things are bad; and there are no guarantees.
I wonder how it was in the days of Nixon and Watergate. Did people feel so hopeless then also?
And there might be a certain amount of anxiety lest one is found to be incomplete in one's orthodoxy regarding the prevailing viewpoint.
We are not in terribly forgiving times; live and let live is not in many playbooks.