At least before the Deutschlandticket (Germanyticket) that allows travel with “short distance” trains the price still was too steep for very poor people to get monthly or yearly tickets (i am not talking about people with jobs) and they walked/biked (some that still want to save money refuse to buy the Deutschlandticket too). Or the infrastucture in rural areas is bad (especially where the AfD/Nazis are strong)