Well I think we were both making some generalizations, but sure, let's talk about rollcages in street-driven vehicles. In a typical Jeep or FJ, you're looking at a pretty basic 6-point cage at the very least. There are a million variations, but most of them extend forward to the A-pillar. I wouldn't consider anything less a rollcage. But I did say that I'd be inclined to put a rollcage in just about any/every vehicle I own. Given an opportunity, I'll always jump at the chance to make my vehicles safer. The way I see it rollcages serve different purposes in different vehicles, but when they're designed right and built well, I think the benefits far outweigh the downsides. I'm not trying to make myself out to be some kind of expert here, but I'll use some vehicles I've built and been involved with as examples, just to further the conversation.
I built several different rollcages for
my old CJ7. The last version was pretty simple, but it was tied-into the frame in a bolt-together fashion so I could still remove the body if/when I needed to. That was a custom frame, kevlar tub, and full custom cage, but it was still basically just a Jeep. Full-bodied and street-driven. It was comfortable to drive on the freeway with 40" tires, and handled respectably for such a big Jeep. As much as I drove it on the street though, I was primarily concerned about low-speed offroad flops. You know what I'm talking about. I could have built a safer cage, but didn't want to have to deal with anything too intrusive. Beard suspension seats and Simpson 5-point harnesses kept me pretty secure in there.
The rollcage I built for my Tacoma was a lot more involved. Different vehicle, different purpose. The Tacoma gets flogged off-road at a LOT higher speeds, and the consequences are a lot more serious if something goes wrong. So I caged it from bumper-to-bumper, with a full interior cage. Also installed a set of Sparco Evo racing buckets and Crow 5-point harnesses. This is also a street-driven vehicle. My daily driver right now, actually. I did cut out one of the door bars to make it quicker/easier to get in/out of, but I think it's still pretty close to a race-quality cage. Oh, and the airbag is still intact and functional.
Here's an example of a rollcage that I can't take credit for building, but had a hand in planning. This HD2500 project was intended to be used as a tow-rig, prerunner, chase-truck, and daily-driver. Tall order, but the rollcage was built so as to be almost completely invisible, and helps to keep things nice and comfortable inside. Airbags are also still intact and functional in this vehicle too.
I'm also planning on installing a rollcage in my
motorhome (some discussion about that
here). This is going to be another simple Jeep-style cage, and will NOT be attached to the frame in any way (the cab is on suspension mounts).
All VERY different vehicles, with different types of rollcages designed/built to suit each of them. But in every case, I would say they're safer than they would be without them. The rollcages in each of those vehicles was built with the type of crashes/accidents that they're each most likely to experience off-road. Beyond that, I think they are all going to be safer on-road too. I'm thinking about the kind of accidents where people are likely to get mangled/killed. You know, getting T-boned, offset head-on crashes, etc.
My thinking is that the rollcages all create some kind of safety capsule around the driver and occupants. No rollcage is deathproof, but I'll take any measurable increase in safety. And I think each of those rollcages adds to the safety of those vehicles.
In the event that I get in an accident in my Tacoma, I'm not too worried about the other vehicle ending up in my lap. In my Jeep, the rocker panels guards (which are part of the rollcage) would almost certainly be helpful if I ever got T-boned. I've seen pictures of accidents where deuce's have been involved in head-on accidents, and their own front axles get pushed under them. The front wheels/tires smashed into the cab. My goal is really just to try and preserve the integrity of the cab, in order to protect myself and any passengers. Rollcages do that. Some better than others. Like everything else, it's a compromise.
I guess I would relate it to the safety gear that I wear when I'm riding my motorcycles. Nothing is going to save me from being crushed or mangled, but I wear an aerostitch suit whenever I ride on-road because I'd rather not grind my kneecaps off and end up in a burn-ward if I go sliding across the asphalt. Not a silver-bullet, but I wouldn't ride naked.
