They want so very badly to appear as though they care and are doing something, but not enough to actually do more than type on a keyboard. Not a new term, but much more prevalent.
On many issues that's pretty much all you can do and some people can't do anything else for various reasons. That doesn't make them lazy or their efforts meaningless. Ever heard of the saying "the pen is mightier than the sword"?
@Magnolia21 not much, but it may still change something. And someone posting here doesn't mean they don't post on more active social media too and aren't making an even bigger impact in other ways.