Because water heating with heat pumps is currently garbage on the residential scale.
Also because we’re already stressing electric infrastructure with what we use now, and few plans to add capacity in any reasonable amount to deal with the massive increase in population, plus electric cars, AC during heat waves etc let alone home heating.
Gas is efficient for heating, and there’s plenty of other stuff we can and need to look at before we replace that.
That’s because you’re using LVM though. In most distros you could also use something like:
/dev/vg/root