They hold the heat, so it burns the shit out of your feet
You need to tip toe around in flip flops (don't get me started on flip flops)
It looks like you are on a construction site
You feel dirty afterwards
There's rocks in the sea (he sand comes from broken up rocks after all).
There's large waves, big enough to break rock into black sand (coincidentally)
The waves and rocks at the sea will make it too dangerous for your kids to play in it.
Combined with the hot sand this means you have to hide in a sun lounger for a few hours.
You can't build proper sand castles
You have to lug buckets and spades to the beach first before you realise this.
Your toddler will forego their midday nap just to make things more uncomfortable.
You can say you went to a beach with black sand.