Complete timetables remain important as they give you an indication of the overall service and the approximate hours of the day that the service is provided.
Whilst I broadly agree I must admit that RealTimeTrains with its filtering options is making even that use of timetables a thing of the past for me. It's very easy to fire up RTT put in an origin, insert a calling at for later in the journey and set it to cover the whole twenty four hour period. It's how I scan for service frequency and the times during which the service runs these days.