Of course the title doesn't have to be a question, as long as it's intriguing. Questions are just easier to do imo.
Example being my, "Why are all these Mario's in the same level?" video. It had poor retention, but amazing ctr
Formula to viral video on YouTube
- Ask audience a question that is intriguing in title
- Deliver answer to said question in first 30 seconds
- Create a hook within that 30 seconds
- Maintain retention through the rest of the video while maintaining topic said in video title