I don't think it has to do with being international or not. It has to do with the fact that groups are generally more popular than solo artists for all audiences. Groups have the following advantages over solo artists:
- A group dynamic between different members makes for very interesting interactions
- More members = more content
- More members = more frequent content
- 5 people doing dancing great is more impressive than 1 person dancing godly
- Can continue activity when one person needs to take a step back (injury, depression, military duty, etc.)
