You're not alone. We had a wonderful UC birth with our third child. It really was an awesome experience and I wasn't really fearful at all. It went wonderfully and I have no complaints....
Which is why my husband was totally thrown off when I told him I wanted to use a midwife with this pregnancy. (Apparently I did a great job of convincing him of UC because it was hard to convince him a midwife would be beneficial!)
In order to understand why I chose to have a midwife after having a wonderful UC, you probably should know a few things.
The area we lived in (Louisiana) had no homebirthing midwives. There were midwives about an hour away from us that did births in their free-standing birth center, but that was it. We used them for some of our prenatal care, but as we neared 30 weeks, we discontinued their care.
I desperately wanted a homebirth. I had two hospital births, and while I did have fairly natural births- with the exception of my first child getting stuck in the pelvis (oh the joys of laboring flat on your back for 10 hours!) and having to be pulled out with forceps- I knew that my births would have been much better and quicker if I had not felt so awkward and uncomfortable. (All those strangers? Being exposed to people you don't know... it's not a good feeling!)
So, I eventually decided that I would have my homebirth without a midwife, since there was absolutely no possibility of that. (I did entertain the idea of having a doula there, though, but decided against it in the end.)
We now live in an area that has MANY homebirthing midwives- and some excellent ones at that.
In Louisiana, my husband was always nearby. He was always in town, and he ran his own businesses, so he could be home at the drop of a hat.
Now he is no longer self-employed, and is sometimes anywhere from 3 to 12 hours away from me (or at least on the other side of Houston... which could take him up to two hours to get home in traffic).
I do not want to have a UC alone. I want someone- preferably my husband- to be there with me. But, something may happen so that he is not able to arrive in time (at least for the major laboring, when I need someone to just sit by me or hold my hand- or hold me up in a standing position).
Also, we have had a real struggle to get our child's birth certificate (ARG, Louisiana) and it would pretty much be done for us by our midwife, which would be a nice big sigh of relief after all the hassle we've been through.
Mostly, it would just be nice to have someone there to help clean up the mess and deal with some of the smaller things while my husband and I enjoy our newborn.
I picked a midwife that is very hands off. I told her I wanted everything I had in our UC- my husband to be extremely involved, for him to be able to "catch" the baby (He even helped the head out so I wouldn't tear), etc. And, because she's absolutely wonderful, she's okay with all of that. She's the sort that will be as involved as you desire her to be.
I think it's also important to note that we had 4 miscarriages before conceiving this baby (I'm now 13 weeks along, and I dont think I'll ever feel "in the clear")... and so I really want more prenatal care and someone watching over me than I did with the last because I am so paranoid about losing this precious baby.
It's hard to explain why someone who had such a wonderful UC would not continue on the UC path with the next birth (and we do desire more children, even after this one arrives).... but we are doing what feels right for the time. I think I need someone to reassure me that everything is okay and is going fine due to all the issues and complications we've had getting a "sticky pregnancy".
Who knows, with our next, we may be back on with UCing.

Whatever the case, I do desire a natural, intervention free birth, and so, whomever is involved in the birth must fit in with that.