Believe me, people will find your server. They find servers that aren't listed, and these servers are publically listed.
And they come and they grief. The kids, the 4chan trolls and whatever you want to call them. I've dealt with it on a number of occasions. Someone places a few thousand blocks of water everywhere, which must be removed by hand. (Unless you're using anti-griefing tools, which prevent TNT abuse, lava abuse, allow turning off certain elements, and give you the ability to rollback a players changes by time).
Anti-griefing in minecraft is like backing up your data. You don't think you need it until all your stuff is irrevocably screwed up.
If you play with fiends you don’t need anti-giefing. (Ok, if you do need anti-giefing even though you play with your friends you may not have the best friends.)
It's basically a service that is not for everyone but very attractive for some. I assume they are working to make those service attractive for more people, but it's a good fundament.