At ideal conditions. As the temperature difference is greater, the efficiency goes down. So right when you need heat the most, gas is still at 90+% efficiency while heat pumps are closer to or under 200%.

Then you have to look at capacity. It can be expensive sizing for the greater temp differences when it usually isn’t. If you have a heat pump that can be 400% efficient, do you really want to pay for quadruple the capacity so that even when it’s at 100% efficiency it still puts out enough heat? No one can afford that