With capturing all of it instead of burning it off will also raise production and lower the cost. So why is it that your glass is twice the size it has to be? Dealing with a problem that is either a glass half full or half empty is not the way one should be looking at efficiency when it comes to dealing with engineering problems.
People have been trying to attack these “engineering problems” with NGVs for at least the past fifty years. Nobody’s solved them all and they’re still not very good.
Capturing it all isn’t even an option with the infrastructure we have now. We would need literally an order of magnitude more pipelines, etc., to even begin to feed the vehicle fleet.