A few reasons. 

- After the 1 or 2 year contracts are up, I can keep my hardware. 
- I need to trust some random company in a foreign country for a long period of time
- These machines look cool and there is a sense of accomplishment
- Helping with decentralization
- It's a project I'm building with my 10 year old son who is just getting into computers for the first time.  He used the word motherboard in a sentence yesterday.