No reason for Wei and Zhao to be sweating and running around to help Han just yet.
With Ouhon and Mouten blocking their path you need an army in the 100's of thousands to get past them and still would have to fight another battle which isn't gonna gain you an inch of territory in return.
Qin has suffered back to back defeats, has a number disadvantage and their soldiers are not well trained so it's best to wait and see if Han can crush them or not.
If Wakua Kan gets defeated then they can move and stop the Qin before they can take Han.