Perhaps it’s about legacy. LX has the history of Swissair behind it with its reputation for quality, good service and hospitality. AFAIK they took on a lot of the old SR flying staff. The old Sabena, on the other hand, always did have a bit of a name for haughty, unfriendly service (although I always found them OK.) Also, in the local context, maybe they always had to be a bit careful about speaking a language which the customer didn’t want to hear, perhaps making them seem a bit distant and formal (??) On the other hand, SR/LX seem(ed) to manage that OK.