You are ignore several obvious.

1) There are strange seal and marking all over the barrel, wouldn't that alone make a ninja stop and ponder what they meant?

2) Yes it's easy to carry a body then a barrel, but wouldn't it be easier for that person to walk? It's pretty suspicious, what if Sasuke is drug and hold stable in that barrel, thousands of possiblities comes to mind. Why risk breaking it open now instead of a later safer time? What if the barrel was a decoy carrying poison gas? What then?

The barrel is so suspicious it's just common senses not to open it until at a safer location, say, within konoha border. With help and without enemy around. Even if someone is stupid enough to break it open, is it truly wise? Is it safe for both the opener and Sasuke? Do they even have time? I don't even think they have the chance to break it open since the sound 4 been on their tail the instant they touch the barrel. Please ... enlighten me to all these staggering questions.


edit: They barely caught up, can they truly risk losing them by circling around and try to set trap with no guarantee they would work? Not one of the genin is a trap master.