Mainly cost I'd say. 20 or 40 years ago, depending where you were, gas was cheap enough that it mostly wasn't worth caring that much, and electric anything was

Mainly cost I'd say. 20 or 40 years ago, depending where you were, gas was cheap enough that it mostly wasn't worth caring that much, and electric anything was the expensive option. Aircon for cooling was a much easier choice. These days it's starting to look hugely attractive both ways, and I think will be ever more so. Cold areas usually have a mostly unused backup heater in heat pumps, for those few times record breaking cold arrives, and of course the nearer you get to a COP of 1 (1kW in = 1kW out) the longer it takes to pay back the extra cost.