Why would southern staes find it so important to keep a balance between free states and slave states

If there were more free states than slave states, then there would be a push for a factory-style economy. The South didn't want this, as their economy was heavily dependent on slave labor. Basically, they wanted a balance between free and slave states so as to preserve their economy.

For the fought for what they belived they also gad high tesion and with high taxes they needed them to make a liveing