I don't think they are always reluctant. I think sometimes they don't know what they need. People often set up a business and think "right, I need an accountant", we need to be there to say "no".
Another problem is that clients don't always appreciate that bookkeeping is a profession. They sometimes know a wee lady down the road who keeps the books for a local business or two at night. It doesn't matter that she's never had any training or fumbles her way through making it up as she goes along, a bookkeeper is a bookkeeper after all.
The biggest group are the "how hard can it be?" group. They've got the software, read a book, they know how to do it. And suddenly a year or so down the line they're in a right mess.