The basic principle behind it, is to lock up Steem into the ecosystem, because it has a positive impact for the value.
Prizes are incentives for participating.

not that I have a lot to get excited about. :-)

Even small power ups are encouraged.

For the next one I will probably make an announcement post. Every month these run.

Thank you for the inquiry, and for stopping by my friend Vincent.
I hope you're having a nice Sunday.