It absolutely is a good thing when security is concerned. WiFi is easy to snoop even if you're not physically in the room, if you know what you're doing. Sure there are encryption standards that are very good to tamp down on this. However, what's even better with LiFi is you must be physically in the room to intercept any transmissions that are being sent.
This is by design one of the largest advantages to LiFi. There are other practical uses as well, but it's not like LiFi is designed to explicitly replace WiFi.