This.
Also, if you can shell online, people could easily write up macros that shelled for them, distribute them among the community, with no online detection filter to catch them.
That would lead to people getting shells while sleeping = a lot of money = economy gets inflated = everyone has BARs = inescapable wall of bullets = dying = bad. Don't die by an inescapable wall of bullets. Stop the idea of offline Graal.
Oh, and wouldn't it be better to 
go outside rather than play Graal everywhere - 
everywhere - you go? I could see a lot of people doing that.
    
        
            | How would they hack them off an offline game, and dont they have better things todo than steal peoples shells? | 
    
 No, they would edit the number of shells in the games files. There's no detection for this if it's online.