There is a much lower number in hackers.
Hacked clients have to update to 1.9, and many people can't be bothered to get the new ones, etc etc.
If you actually look at the annual graph, a month ago the quantity of bans sharply decreased. That is because we updated to 1.9 (around March 3).
Also, we are banning between 1-4 people a day.
Every day I came online in 1.8 there were at least 10-15 people banned - JUST in the time I would be online in that day. As you can see by the days with top bans, we fairly consistently banned 70 a day during the summer.