No they use them because they are addictive, intentionally. But they reinforce negative emotional content because it is more engaging. This is what causes all the polarisation in society, what gave us Brexit and Trump. See for example the book Careless People, it describes how Facebook set up a huge consulting operation with the Trump campaign to get him into office.

But they are bad for society, it's not for no reason that a lot of countries are trying to ban them for the younger generations now, similar to smoking.