> The question that nobody seems to
    > be willing to ask is the following:
    > who cares?

I think a lot of people are asking that question, and the answer seems pretty clear to me: people care because this echo chamber effect seems to vastly increase the divide between groups. It makes it easier to dismiss opposing views as crackpot and evil who disagree because you're always surrounded by a steady roar of agreement. That increasingly bitter divide, and the accompanying increasingly entrenched and unswerving beliefs, are things I find deeply worrying.

Social media didn't invent this, of course, but it's made it much more prevalent.