The insurance company doesn’t give justification for why they don’t include those countries in their offering. (Or why they don’t include other countries, outside of geographical Europe).
I could only guess that it is something to do with the legal agreements between Switzerland and Norway and the EU. (We often heard Norway and Switzerland held up as potential examples of what Britain’s relationship with the EU could be like after it leaves the EU).
But ultimately the insurance company can offer to insure whichever countries they like. For whatever reason they like.