Car safety standards have been rising for decades. Crush zones, offset steering columns, and airbags are just a few of the safety features of modern cars. In time we may well end up with a 4-pt harness assuming it can be shown as much safer than the 3-pt was have now, which includes usage. This thread is addressing part of the problem. You don't even want to make a required 3-pt so why bother talking about a 4-pt? If fewer people would use the 4-pt, then it obviously isn't a good option at this time.