My non-European partner gives money to their parents despite being fairly middle-class and fiscally stable. You're right, it's cultural - theirs expects grown children to contribute to the parents after spending their childhood paying for them. It's an investment into the family unit as a whole, as the family will support you beyond what the state welfare could provide. Had a car accident and need some money? The family can help. Want help with a deposit for a place? The family will contribute.