Very Low Hostile Mob Spawn Rates

Started up a new world ( seed: 767004949293730)

on my first caving session of about 1 hour I haven't seen any hostile mobs.

I checked at night on the surface and even there I could not see more that 2 Zombies and 3 Creepers.

 

I attached my whole world folder.

 

Happy to help more if possible.