The physics is that if it's gaseous at low temps, then it has excessive pressure at room temperature so the canister has to be excessively heavy to not blow up.
Relatively few ultralight, low temperature backpackers so not a lot of money to be made.
When it burns, the (iso)butane produces a lot more heat than is required to warm it up a little so it evaporates. If you could just get a little of that heat down to the canister, the pocket rocket would work down to very low temperatures.
Like if you had an aluminum windscreen attached to the canister, going up into the flame, some of the heat would conduct down to the canister.