Presumably because the idea is to save money, and a call center forever would be more expensive but the far more realistic issue, if unlike an AI that could provide a consistent on brand experience, with a call center your experience would be hit or miss every time and drive thoughts are already not usually a great experience so a low wage call center would probably be even worse. Taking away jobs is certainly an issue in itself but I imagine overall this will mean a more consistent experience that they can improve over time.