I used to think the same.. but this month i did an experiment that changed my view on this topic a bit: I had two design clients and they had a clear vision of what they wanted done - really abysmal stuff IMHO (logo design), but i did it.
But i also (which i don't usually do) showed them *my* version and what's probably more important, i EXPLAINED to them, WHY my version would be the better choice. Both clients ended up purchasing my version of the logo.
So, i think it has a lot to with communication skills and how you present your alternatives. No one likes to hear "your vision sucks" - but plenty of clients are open to alternatives, if presented in a friendly way.
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