My 2 pence worth
I don't take my 'bolt' in rear roll bar out when driving on the road.
My 'bolt' in conforms to MSA regulations which is good for 10 sec runs.
My terminal speed is 125mph
The shoulder harness fits to roll bar and is SFI approved, this 5 point harness is also fixed as per MSA regulations with correct floor mounting points fixing bolts etc.
When racing i wear an helmet, i don't when driving on the road, but if i decide to give it some beans i tighten the harness to keep me well fixed to the seat.
I know there would be some head movement if anything happened but i don’t think many people would wear an helmet 'just in case' anything happened.
I'm 5'11" and have my seat well back, the seat mounts i use are lower than standard which gives quiet a bit of room between my head and the roll bar.
The door bars i have are removalable (again MSA approved) and make life a lot easier when not fixed.
I do get an extra feeling of well being when driving the car quickly with the roll bar and harness fitted compared with out.
When i realised the speeds and times my car was doing i didn't take much persuading to have these fitted, but i wanted a 'bolt' in and this wasn't easy to get or cheap that meets the MSA requirements. Certified tubing meeting the required sizes, welded by certified welders, construction to meet requirements and fixing points as per recommendations.
These can all be found on the internet or by going to an approved specialist for roll cage/bar construction.
So Yes i am a fan or roll cages/bars but i don't use my car as a daily drive so i haven't voted
I do think that if you had a big off a roll a cage would help IF you had a good harness properly fixed, and good seat again properly fixed and most importantly a well constructed and fixed roll cage/bar
Just my thoughts