Gas has been the cheaper option for so long, and I think a lot of people mistake that for efficiency. The idea that something can be both less efficient but also cheaper seems counter-intuitive.

Until very recently gas appliances were the sensible option because the cheaper running costs more than made up for the increased up front costs (unless you are a landlord and will be pushing the operating costs to someone else). That has also changed, which I think a lot of people also haven’t caught up with.