My reason for picking it is this. Rapid way to get to MvP without concerning yourself making a site presentable. The defaults look good and most importantly most of your customers won't know or care.
Once idea is proven, and tech is built then I will move onto fixing the way it looks (most likely pay a designer)
I guess that is exactly how it makes me feel, like I am dealing with a prototype and it is somewhat less trustworthy...
You get the core functionality because you are an early adopter (e.g. Hacker News user). The frills and marketing, such as the custom design, is what will acquire customers like your friends.