According to a 2006 Bloomberg article:
Finally, there is the integrity of the passenger compartment.
Years ago, most vehicles had steel A-pillars to support the roof.
Today, it is the windshield that provides much of the support that
prevents the roofs collapse during vehicle roll-overs.
The Complete Guide to Auto Glass Installation also discusses this issue from a litigation point of view, saying that a California woman became quadriplegic in part due to failed bonding of a windshield, causing roof crushing during rollover of her minivan.
This case was Rhyne v. Windshields America.
Transcript of 25 February 2000 20/20 TV show:
ARNOLD DIAZ (VO) Four years ago—Charles Rhyne had the cracked windshield on the family’s minivan replaced at a local glass shop. Seven months later — on a rainy California highway — the minivan slid off the road, his wife Tracy behind the wheel.
CHARLES RHYNE We were rolling. And when the vehicle stopped, I couldn’t move.
ARNOLD DIAZ (VO) The replacement windshield had popped out during the rollover allowing the roof to buckle into the passenger compartment— breaking Tracy’s neck.
TRACY RHYNE If that windshield had reinforced like it was supposed to-I would have had at least four to six inches clearance.
ARNOLD DIAZ Do you think about that?
TRACY RHYNE All the time.
ARNOLD DIAZ (VO) At first this mother of three didn’t want to believe it when doctors told her the accident had left her a quadriplegic.
TRACY RHYNE When I heard it from Charles, I knew for sure that — that it was true. And I wasn’t going to be able to be the same kind of mommy or wife. My life had totally changed in a matter of a day.
ARNOLD DIAZ (VO) The Rhynes sued the company that had installed the replacement windshield and settled for 2 million dollars.
CHARLES RHYNE They forgot to put a secondary primer in the installation of the windshield. So that the hardening material when they put on the windshield — it didn’t harden.
ARNOLD DIAZ (VO) Experts tell us windshields are often improperly replaced because many technicians are either sloppy or haven’t been trained well enough. So we decided to see for ourselves. We had windshields replaced in three different cities.