Germany is not a direct democracy. Theoretically it could be that 100% of the constituents oppose these protections, but still elected MPs which support them. There are plenty of issues that are more important and more likely to influence one's vote than the price of taxis.
That's not true. Elements of direct democracy are for example available at the local level. Here in Hamburg the politics is supporting it. For example the mayor of Hamburg is openly supporting it:
I'm fairly sure that this is not possible to enforce via Volksentscheid. Its state legislation, so the details differ, but as far as I understand in most states the referendum can only decide over a proposed law. In some states a general guideline for the parliament can be decided over (Berlin, HH and Schleswig-Holstein) but those are only recommendations.
I'm not certain if it would be a valid course to create a law that forces the parliament (or rather the states representatives in the Bundesrat) to propose a law. That might create a legal problem: What if the proposed law gets changed or rejected in the Bundesrat etc. You're free to try, but I doubt that course of action will work.
