You're right! I didn't realize individual workers and informal unions had a right to strike.
But their protections are a lot more limited than public unions, like the teachers or police unions. If you're striking for better pay or conditions, it seems you can be replaced and, depending on circumstances, fired without legal repercussions, whereas if it's for unfair labor practices, you have more protections.
But you do have a lot more legal protections than I thought, so that's good to know.