Lead Propeller and Investor Carrot - how does this work?

[Jessica Freesia]

Hi, I'm looking at these companies and really not understanding the basic facets of the business model.  

Why is this a subscription service instead of set up as a one time fee?  

What services do they provide after setting up the website?  

Would I own the content of the website I build or even the domain if I use these services?  

Are they transferable if I decide to discontinue service?  

Thanks