Ram Fender Foam

Why does Ram continue to put foam between the inner and outer fenders on the bed? When I repaired my '02 the foam was clearly the reason for the bedside rust. My '14 has the foam in it as well. I understand the purpose but it is a huge risk for rust. Tonight I soaked the '14 in WD40 and will continue to do so in hopes of warding off problems.

I believe it's actually a seam sealer.

It's put on just before the marriage operation the spot weld the inner and outer bed sides together.

I think that it looks like foam because the spot welding process boils it.
It's that or it expands to foamlike when it's in the paint ovens.
It doesn't look like foam when it's applied, it looks like caulk.

Problem I see it that it's applied when the panels are bare metal, before it's been dipped in E-Coat (Epoxy Primer.
So there's bare metal which invites future rust problems when water gets under the sealer eventually.