The Allstar and Launch reports give different reasons for Anthrax leaving the tour. 

The Allstar report attributed the departure to money with a statement from Motley Crue, "Due to financial constraints, Anthrax will not continue the Maximum Rock Tour. The tour will continue with Megadeth and headliners Motley Crue."

In the Launch.com article, Motley Crue bassist Nikki Sixx said, "Anthrax is off the bill. It saddens us because they were the band that really lit a spark in our ass every night. The biggest complaint is that we haven't been playing long enough for our fans -- and it's our tour. So we want to add five or six more tunes, plus it gives Megadeth some more time, too. There just wasn't enough time. I'll miss them. They are amazing." 

The webmaster of Anthrax's official website had this to say:

" ANTHRAX has left the Maximum Rock tour and cancelled ALL remaining dates for this summer. Anthrax was just as stoked to see their rabid fans as you were to see the band, and are totally bummed out to be packing it in for the summer. You know what they say about the 'best laid plans...'" The guys will be taking a few weeks off, then head into the studio to write and record what they assure me will be the greatest album since Poison's Look What The Cat Dragged In! :-) Hang in there! Oh yeah, next tour Anthrax is going out in Apache helicopters and humvees as the Heavy Metal Special Assault Team. Anybody cancels on us and we go Basra Highway of Death on their ass." 

He concluded by asking the fans to demand a full refund if they had purchased tickets to see Anthrax.  " GET YOUR MONEY BACK BY ALL MEANS NECESSARY!!!" urged the Anthrax webmaster.