German hospitality: What's up with asking me to bring my own whatever?

I have a question out of genuine interest: What is normal when it comes to hospitality toward visiting family?

Background: I live in Germany and I consider myself pretty well integrated in almost all areas (deutsch kann ich auch, und kann sogar das Wahsystem inklusiv Überhangsmandat erklären). However, one area where I still constantly am surprised or fail is in hospitality.

The thing that triggered this post: I have a health thing that means I can't eat salt with Iodine. (Jodsalz). Is it normal, that a household of people born and raised in Germany would expect me to bring my own salt? if so, why? This goes for both short visits and longer stays.

This is not a loaded question. I ask because my limited experiences cannot be seen as representative, and I am genuinely curious what normal hospitality is. I really want to understand the attitudes and assumptions so that I can be a better guest. I've noticed other differences, like not being offered food when hanging out at a friend's house when it isn't explicitly a meal invitation (weird where I am from). So, if you have a non-salt related insight, that would also be appreciated!