You hire a plumber because they're an expert. You don't want small issues with something that can lead to bigger issues down the road. It's the same with a graphic designer. You can get something cheap and quick done, and then when you go to get it printed it doesn't work. Maybe you send it for screen printing, or try to place it on a coloured background, or so many other things you should be able to do with your logo, but it doesn't turn out anything like what you thought. Do it once correctly and you won't have to do it again.
I don't design materials for my portfolio. I design for my employer and my clients. We sit. We chat. My goal is to get what's in your head out with the tweaks and expertise I can add in to make sure it's amazing. It's a partnership. We'll bounce ideas back and forth.
In the end, my goal is for you to be happy, to be educated in the process and to receive better than what you envisioned. I want you to end with something that is completely usable and saves you time and money down the road.
That's it. Simple.