I had this very fruitful conversation about the inertial motion of charged particles on gravitational/electric fields.
A field force like gravity, can't be felt, it does not produce proper acceleration, nor it does do work on a mass - because its just spacetime curvature you are falling into, and it does not deliver (in first order) energy to you. If you are blindfolded (no external references), you can't tell if you are on a geodesic of the gravity field or standing in empty space, you are just weightlessness, moving in an inertial referential. Gravity produces no internal compression or dilation on you, so your accelerometers measure zero.
On the other hand, contact forces can be measured by accelerometers, they do work on the object, and promote the object to non-geodesical trajectories. Accelerometers are only able to measure contact forces, not gravity force, because gravity is a field force that acts on all of you at the same time. Contact forces on the other hand act layer by layer from the contact surface on through the body being properly accelerated.
But contact forces are in ultimate analysis are just electromagnetics forces between the atoms of two distinct bodies of matter. I understand (see here) that everything that carries energy and/or momentum do produce a curvature in spacetime.
So, both masses and charges$^\star$ produce spacetime curvature, but we see gravity as a force field that acts on whole bodies at once (and thus cannot be measured by accelerometers), while electrostatic force acts like a contact force we see acting on layer by layer of a material, acting to promote proper acceleration, and thus renders objects to non-inertial frames.
So, what is the fundamental differences between these two? Is it the fact that gravity has a much larger range than the electromagnetic force. Or is it some more fundamental reason?
$^\star$ Charges produce spacetime curvature indirectly due to both their masses and the electromagnetic fields they generate.