A smart light switch must have a neutral wire. It is because the switch needs to be powered so that it can be connected to WiFi. There is a way to wire it without having a neutral wire, but it is in fact dangerous. It basically energizes the ground wire so that the switch can receive power. The problem with that is if you or someone else is working on a different circuit, the ground wire is energized and could possibly cause a shock or a fire. If you do end up doing this, whenever you work on any circuit in the house, you need to switch off the entire house from the main breaker. Kind of a hassle if you ask me since sometimes you may need light or power tools as you work on a circuit. You don't necessarily want to turn off the entire house rather than just the one circuit you're working on.