Check the FAQs under ViteX section of the forum:
What's the point in staking vite then?
Hmm I posted a link. You can read more about what you can do with quota.
Will be the quota transformed in vite tokens as a reward?
Because otherwise I could simply run PoW (voting nodes) all day and get my vite tokens anyway.
You could do that because you're a light user. For power users who send out transactions every few seconds, or thousands per minute, clicking Run PoW everytime is time consuming and just not as smooth. Also Run Pow only grants just enough quota for basic operations (only performing transactions or voting). For advanced operations, you will be required to stake to generate more quota.