Is the plastic/rubber trim-looking stuff along the sides of my windshield, and now all cracked/crumbling from the sun:
1. Cosmetic only?
2. Weatherproofing?
3. Holding my windshield in which is now in danger of falling out

 

Welcome to the site.
The windshield is urethane adhesive bonded to the body.
The trim is a dress piece to close the gaps and doesn't add to bond or hold strength.
Some windshields will have a bonded flexible trim/lip that is bonded to the backside of the glass edge all the way around that closes the gap, but they, the glass, are still bonded to the metal framing.

 

Ok, thanks!