Entrepreneurs who can sell themselves and their business make our job easier, so we might be willing to give you a break. If you're like most executives and entrepreneurs, you're just plain too busy. We can get it done faster than you can. Most managers have the expertise to do only part of the plan, and they have to make-do on the rest of it. Also, we may be more objective in our language than you are.
Most investors relate better to the latter.
And finally, maybe you shouldn't pay us to do it. If you have the ability and the resources to get it done in-house, it would be bad business to hire us. It depends on the type of fundraising you want to do. The plan we produce is a complete document, with financials, market research, description of capital structure, etc. We don't guarantee things we can't control.