Why is normal force due to gravity regarded as contact force? We know that normal force is electromagnetic in nature. Then why is normal force said to be a contact force?
 A: We know that on the sub-microscope level the forces are electromagnetic, but in the world we perceive, we say that if two surfaces are exerting forces on each other, they are in contact.  It's a matter of the definition of words.
A: Fundamentally all forces are field forces. Electromagnetic, gravitational, the strong and weak nuclear forces. Meaning, fundamentally, contact forces don't exist. Contact force is a term invented for what we experience at the macroscale, not a description of an underlying fundamental behaviour.
A: This question seems to be easy but it’s answer is related to
one of deepest mysteries of Quantum Mechanics . To answer
this question let’s ask a more fundamental question. What
does it mean “to touch” or what is a contact? Well this
questions doesn’t make sense at macroscopic scale . Let’s try
to understand it at microscopic scale – The Quantum
world.So for making a contact the atoms of two object
should get closer and closer and closer and the
electromagnetic force will oppose that but even after that
something is still on the way- Pauli Exclusion principle . This
principle was formulated by Austrian physicist Wolfgang Pauli
in 1925 initially for electrons but later extended to all
fermions. Fermion is a category of elementary particles. The
name fermion was coined by English theoretical physicist
Paul Dirac from the surname of Italian physicist Enrico
Fermi.So now we know Electron is a type of fermion. Let’s
look at the general statement of this principle which states
that no two identical fermion particles can be in the same
quantum state. To make electrons in contact their quantum
states in an orbital has to be same which is a direct violation
of pauli’s exclusion principle. The electrons as well as protons
and neutrons that make up ordinary matter cannot get close
enough together to allow this to happen, especially under
ordinary circumstances.
Now the question is what prevents contact. Is it EM force or
PEP. This is a very debatable topic even for high level Solid
State Physicists so we are not going to dive deep into that but
now we have enough information to ans our original
question . The cause of all the contact forces are
Electromagnetism( or in a sense PEP ) . Contact forces are not
fundamental in nature they are a part of one of the four
fundamental forces of nature.
