occupy first row of bleachers?

[jodibuck]

I was advised by a veteran volleyball official that the first row of bleachers should be vacant for all varsity volleyball contests. I understand that players are allowed to "play to" the bleachers, but I can't find it anywhere in the rules book that states spectators can't sit on the front row. He said it was a safety issue.

[SNIPERBBB]

What's the safety issue? Pretty sure people are generally softer and less hard edges that empty bleachers