It is very important; security, backup, maintenance etc...
The problem is there are two kinds of customers, cheap and cautious. Cheap only wants to pay $12 a month.. and does not understand or want to understand that not having maintenance is a bad idea. The cautious ones pay anywhere from $50 to $500 for a managed WordPress web hoster for their site. Why would they trust you? So what you are saying is that you want to educate the first group to understand they need help or get the second group to trust you more. Both are very hard sales... What I do with both these groups is sell them management included in the price of the full package. I don't know if your doing something else here. Another interesting Idea that I had, but don't have time, if your really good with fixing WP, let them break it and then charge them to fix it... Might be an easier sell.