I firmly believe in the idea that people should try to do something by themselves and seek any and all help they can get from others who've already gone through similar things so that they can learn themselves.
You say you don't explain the installation process, that you just do it and let it be. In as much as that can be complicated for some, the customization of the blog that inevitably comes after is even more so. And people who don't have a clue as to the layout of files and things as such will have an extra hard time.
There is nothing wrong is trying something out, stumbling parhaps, seeking help and learning how to get things done.
If you offered a full-fledged service that not only included installation, but installation of themes and plugins and most importantly explained the whole process step by step to your "customer", then I would say there is a lot of value.
If people just want to blog without having to worry about the intracasies of maintaining their own domain and the software that runs on it, there are enough services out there for that. But when they take the role of being their own webmaster, I just think they should go all the way and not half-ass it.
P.S., and oh I'm not really concerned about whether this is a ratified thing as far as Matt or others go, I'm just more thinking along the lines of "teach them to fish...", if you know what I mean..