Dave Trott, as always, nails it. In a client/supplier relationship, the challenge is to help the client understand the challenge and then solve it with your solution without realising that you have taken them on that journey. That is truly difficult. 

I am reminded of a story of a creative pitch to a property company that was building and marketing a mid-range residential development. Colours in Asia are very important and have social meanings. He finished his presentation, which had been approved by the Marketing Director, and asked for questions. "I want it in gold", said the Chairman of the business, referring to the colour scheme for the creative work. In IndoChina, gold means luxury and this was not a luxury development, so wholly inappropriate. "Of course", replied the Creative Director, "Why didn't I think of that, thank you for your advice". And so it was developed in gold and they retained the client. To try and advise against gold would mean loss of face for the Chairman and the loss of the account for the agency. 

Sometimes to win, you need to be practical and consider the bigger picture.