You want every last immigrant to be personally interviewed? Do you know how expensive that process would be? They interview ones that are flagged for concerns. That's enough, imo. You're not going to make the country any safer by interviewing everyone, considering crime amongst immigrants is lower than the native-born population anyway. What's the purpose? To test their language skills? That's already done in the first phase before they even move onto the security screening and it's done without an interview. Interviewing everyone is way too expensive for the returns to security or even linguistic competence.