Two seconds of googling shows that the NTSB states 95.7 of passengers survive, and setting aside those instances where no one has a chance of surviving, you have a 76.6% chance of surviving. I read an article the other week of a similar study (though I can’t remember where at the moment) that basically stated those who wore their seat belt and assumed the crash position had significantly better odds of surviving a crash than those who don’t.
Seat belts make a significant difference, as they do in cars. There are other variables that make a difference … where you sit (those within 5 rows of an exit have significantly betters odds of surviving, post-crash), plane size (bigger planes are better since they have better energy absorption), and even age, gender, and weight (it’s a lot easier for young, slender men to survive a crash – they are better able to maneuver and address obstacles than an old lady might be or someone significantly overweight).
Cars might have shoulder straps or harnesses, but they are easily able to attach those to the frame of a vehicle. You can’t really attach a shoulder belt to an airline seat without further reinforcing the seat (adding size and weight in the process). That will cost a lot of money in retrofit, (probable) lost revenue from fewer seats due to the larger size, plus extra fuel costs for the heavier seats.
To address OP … Airlines retain the older lap belt tab release style for, I suspect, a couple reasons.
One, it’s better able to hold up against something known as inertial unlatching. This can happen with the push-button release, where the inertial forces act on the release mechanism in such a way during a crash as to release or break. This is a lot less likely (possible?) for end-tab release buckles, like on plane lap belts. I’m pretty sure cars don’t use these because they’re superior, but because they’re cheaper. They may work well in most vehicular accidents, but I suspect they’re less able to hold-up to the forces of a plane crash.
Two, it’s just easier, from the use an maintenance/upkeep standpoint. Think about how finicky some car seat belts can be…and that’s just with one person using it. If thousands of people used a car-style seat belt each year, I expect it would develop mechanical issues pretty quickly (that is to say, someone would break it pretty quick). Simplicity in this case helps cut back on costs.
There might be better buckles and better seat belt styles (there’s a reason harness belts are used by flight crew and required in smaller aircraft), but the cost of implementation can be pretty prohibitive when you consider making them across an entire airline fleet (or the entire industry).
