Bad weather is certainly a factor in a lot of General Aviation accidents. VFR into IMC (Visual Flight Rules, ie you fly by looking where you're going; into Instrument Meteorological Conditions, ie you can't see very far due to low cloud or nightfall) kills a bunch of people every year. Some of those killed are IFR rated. In
theory they know how to fly a plane when you can't see where you're going, but theory and practice are different.
One thing that's different between GA and driving is that you could stop driving. An hour from home, realising that the road really is too treacherous, you could pull over and walk. Up in the sky they don't have that option at a moment's notice. But one thing that's exactly the same is mission mindset - people fixate on what they intended to do until after it's far too late rather than have contingency plans.