Uh ... I am NOT any expert on this but do you seriously think that one of the most fundamental experiments in quantum mechanics has been created and explained while overlooking something so fundamental?
Questioning things is all well and good, and I don't mean to suggest otherwise, but I think a much more healthy formulation of your question would be "why is it that the gravity of the slit material in the double slit experiment doesn't cause the electrons to quiver and thus be the source of the apparent wave effect?"
EDIT: to put it very starkly (and perhaps unfairly so) the wording of your question and my restatement of it can be read as
"Are physicists stupid enough to have overlooked ..."