Usersettings not recognised as text?

Why this expression returns false: CONTAINS([Adresse],(USERSETTINGS(“Rue”))?

While this one returns TRUE: CONTAINS([Adresse],“Marie”)?

For the following values:

USERSETTINGS(“Rue”) = Marie

[Adresse]= 27 RUE MARIE-CECILE

May I ask where do you use it?