Yes, sometimes clients don't listen. That may even be the default for a new relationship. But as a first attempt you should, I think, try to convince them. I'm definitely against the "I told them, they didn't listen, but after all, it's their decision/their problem" approach. But sometimes even that doesn't work. In those cases I think one should lay out the options (including the one the client wants to go with), enumerate all the pros and cons of each, make a suggestion again ("based on this I would go with....") but then let the client make the final call. Just be sure that they really understand the compromises and then evaluate the consequences when it's time. That can work wonders.
After being "right" a few times ("well, it turns out that you were right and we should have done this instead of that") they will listen by default. Better yet, pick up and learn the thought process. Now I quoted right, because it's not even necessarily true: just because their approach failed (or seems to have failed) doesn't mean that yours would have worked better ;). But, of course, since you are the professional, it's more likely and the lesson really is just that.
I had a client once who listened but declined every single suggestion to improve things - including the most basic "Perhaps stop sharing the same root password to all servers and each developer has their unique login?"
It's rare but some businesses just don't want to change if their current legacy processes have made them so wealthy.