LIDAR has obvious benefits.
Even if you believe that FSD can be solved by vision only, LIDAR is an excellent failsafe.
This is what happens when you rely on vision + radar: Autopilot doesn't detect a truck partially in lane :( : teslamotors
Which is why I think Tesla will eventually incorporate LIDAR into their cars at some point in the future. Even if it is not strictly required, it will still be very useful as a fail safe. And considering Tesla wants hundreds of thousands of cars on the road to be FSD, having a good fail safe would seem like the prudent thing to do.