Here's why:
* Common nouns are general names for people, places, things, or ideas. They are not capitalized unless they are the first word of a sentence.
* "Strikes" refers to a general action of stopping work, or a specific instance of a strike.
Examples:
* The strikes lasted for weeks. (general use)
* The strike at the factory was a major setback. (specific instance)
Let me know if you have any more questions!