I can't recall ever being on a flight where the lights weren't dimmed for takeoff and landing? Surely even in full sun the emergency lighting and exit indications would be more visible in a dim smoked filled cabin if something were to happen? (I know, the cabin lighting would probably be out if something that bad happened anyway, but why not improve chances?)
Also... fluorescent light isn't enjoyable, can't see any reason to keep it on full bright even for a flight that's only an hour long.
Also... standardisation, less chance of it being missed for night flights if the crew are used to dimming the lights at a certain point in the same pre-takeoff sequence every flight.
Just my 2c.