personality or personalities

[phoebemia]

Hi, I read the following sentences on a website: (the link is here)
1. The characters' names reflect their personalities.
2. People’s clothes are often an expression of their personality.

Why the second sentence doesn't use a plural form of personality? I get confused when these plural and singular conceptions mixed in one sentence.

 

[Barque]

Why doesn't the second sentence doesn't use the a plural form of "personality"?

The second sentence could have used "personalities" but it so happens that "personality" works too, possibly because it reads naturally with "an expression of".