Welcome, and congratulations, Stacey!
Unassisted birth...there are a lot of reasons. But to touch on what you mentioned...in some states lay mw's are illegal. I prefer not to ask someone to commit a crime on behalf (not that I judge anyone for that at ALL, just saying it violates my personal conscience). CNMs can attend homebirths in my state, but they don't, due to no doctor back-up.
Even so, many mw's are unwilling to simply sit in another room while you give birth. They are liable, you see. The State expects a certain standard of care from them. Some will do it, some will not.
Many mw's are just as medicalized as any OB...in fact, I believe that there are OB's who are more hands-off then some mw's.
There are some really hands-off mw's out there. But many UC'ers believe that even some of the most benign interventions, even a mw's *presence*, changes the dynamics of birth for a lot of people. I know that is true for me. I am perfectly willing to give up my power when vulnerable, to someone who appears to be helping me.
I hope that answers some of you questions.
Oh, and how sad your mw died so soon after your birth!