Because others exist
However it was just an example of an emergency where one might strongly desire to update a broad range of friends and family quickly. Other situations might be natural disasters or a house fire where one "We're alive!" post might require a follow-up the next day with more details, needs, or grief.
It's just to say that an unyielding, global rate limit would not serve peoples' interests well.
I'm personally okay with seeing products that have well-intended friction built into them.
So when one of my 2 score aunts and uncles has a medical emergency, nobody wants to play phone tag around the world, even with group text messages.
Point being, even people without huge families like mine sometimes have big social groups.
You choose the right tool for the job. If a friend is in critical care at the hospital with life threatening injuries, do you really think "slow social" is the appropriate service to use? That's just being silly. As the name suggests, this service is designed for the opposite type of communication. It's like complaining that Sharpie markers should make thinner lines because sometimes you need to write complex notes. Or, that Ferrari should modify their cars because sometimes you need to tow a boat.