Are there any mathematical suggestions/insights/explanations? (I'd hope for a written explanation/interpretation rather than a long string of formulas!!)

I'm pretty sure no one knows the physical reasons for this but am wondering if the equations of general relativity compared with maxwell's equations, for instance, offer any suggestions or insights. There are similarities between electromagnetic and gravitational field formulations but differences as well...are there hints in those differences? Seems interesting that the three forces (strong,weak, electromagnetic) we have unified mathematically can all be shielded yet gravity cannot. alpha,beta,gammas rays, photons,etc. can all be shielded...."gravitons" apparently cannot.