It has been a while since I last sat on an industry jury. I have done quite a few, like those from the International Festival of Media, and the Cannes Jury as well as some domestic industry jury's.
Why do them? To learn!
Obviously, the teams sending in submissions do so because they feel they have delivered something unique and captivating for their clients. They are proud of their work, and want to see how they measure up to their peers.
For me, it offers a unique opportunity to see where the industry is at. If the work is great, either from one or two entries, or the sector as a whole: hurrah! But if the work is just kind of "meh", that provides excellent insight, too. If "meh" is where the participants are at, it tells you that they themselves, their work environment and perhaps even their whole section of the industry is "meh".
That is useful to know when it comes to finding agency partners, judging agency proposals or assessing agency performance.
So when it comes to "jury duty", I am a fan.
(Sadly, I have never been called up for actual Jury Duty. I so want to be in a court room to hear a real life "objection, your honor". I am still holding out hope that one day I get called up...)