The reason I haven't submitted any entries for global bans is because of the tedious process necessary for an admin to submit them. I have several that have been on my "ah, I'll get to it tomorrow" list for a while now.
Most of the information is already in the database. A link could be provided to submit a request for the ban you're currently viewing to be a global ban. That would take you to a form where you could upload the full log file and fill in any missing information and submit. It would reduce the cutting and pasting necessary at the very least, and hopefully encourage more submissions.