What can be the reason behind Microsoft graph API(/v1.0/me) returning NULL in “preferredLanguage” field in the profile object?

My app on Microsoft Teams is using the consent flow to get the permissions from a user. Then with the access token returned by Microsoft, the app is trying to fetch the profile of the user using the /v1.0/me route. But for many users the preferredLanguage field in the profile object is null, only in some users the filed is returning a language. My app needs the preferred language of the user to show a translated version of the app.

I am requesting the following scopes from Microsoft.

1. User.Read
2. TeamsActivity.Send (not related to this issue)
3. offline_access (for refresh token)

Following is the code for the request for fetching the profile.

const { data, status } = await axios({
      method: 'GET',
      url: `https://graph.microsoft.com/v1.0/me?$select=id,mail,displayName,givenName,businessPhones,preferredLanguage`,
      headers: {
        Authorization: `Bearer ${accessToken}`,
        ConsistencyLevel: 'eventual',
      },
});

Below are the screenshots of Microsoft 365 language settings and what the API is returning.