Also rice doesn't grow anywhere near Germany. Today that's not really s factor anymore, because it's so easy to shop, but my parents both grew up sticking very much to a local and seasonal approach to cooking, because everything else was new to them. They eat what they always knew best, so 5-6 days of the week the starchy side were potatoes. Rice is way more filling by transportation effort, but potatoes have been around their entire lives and in my dad's case also what his parents grew on their farm.