In electrical distribution, there are plenty of alternatives, I’ve worked with electrical utilities for a little. In that city, most residential transformers and some legacy switchgear (some up to 80 years old) use mineral oil. In the 90s SF6 switchgear was common to be installed, but the current models of medium-voltage switchgear have neither. And some modern commercial alternatives are appearing for transformer winding isolation and coolant.

The issue comes with higher-voltage switching, such as at substations. If you want to use air separation there, then you’ll need lots and lots of space between to prevent arcing. Since that is not always achievable, that’s where vacuums or agents like SF6 are used instead.