Most clients think you are a magician who will come along, wave their magic wand and they see the money rolling in straight away.
The major issue is that you usually get called in when the business is on it's last legs and you have been called in out of sheer desperation to provide an instant no cost solution. If there is a bad attitude prevailing in that business and there is also a chronic lack of funding available, then no magic wand is ever going to pull that business back from the brink.
One of the major problems is the client thinks they already know it all or have already tried and in your extensive list of actions they spot something painfully obvious that they should have done years ago but never bothered doing, or they had a half-hearted attempt at doing it, so they home in on that one item and begin braying that is not what they are paying you to do - tell them the obvious, while at the same time ignoring the remainder of the wise advice. Or, they cherry pick the option(s) they like the look of and then moan because the strategy isn't working for them. Many is the time I have spent more time changing attitudes and prejudices than actually getting on with the job I was supposed to be doing, but once that barrier is broken then success for the client really is just around the corner in most instances. All too often I have felt like (but not doing so) telling the owner that the business would really take off and fly if they went on a cruise - for around 10 years or so