Untangled Photon - Commonplace or Fictional?

[ObjectivelyRational]

Everyone speaks of entangled photons and entangled states as if entangled photons were rare in nature, products only of our investigations into the quantum weirdness.

With the intent of confirming whether or not this is true according to modern physics, can someone explain how truly "untangled" photons (not entangled) are formed in nature and whether or not they are actually more numerous than the mysterious entangled photons.

What is the common mechanism and how does it lead to an untangled quantum state?

 

[Vanadium 50]

Everything is entangled with everything else. But as as in The Incredibles, "If everyone is super, then no one is", when entanglement occurs across billions of particles, you can't really see it. The experimental trick to see entanglement is to keep a two body system from getting entangled with the outside universe.