Because we fought a war to stop it from happening.
I'm talking about if we let one go unhindered, then the principle that Madison postulates that if equal states decide unilaterally to leave, then that implies the power of other states to kick out a state (the mass seceding from the lone). That would lead to tyranny when a majority of states chooses to oust a minority state (e.g., abortion states banding together to oust a pro-life state).
What I would support is a Constitutional amendment reversing the process, that is, a process for a state to appeal to Congress for permission to leave, requiring the same vote as required to join.
-PJ
One state leaving would not cause the union to fall apart. What it would do is make clear that every other state had that option.....ie that the union is VOLUNTARY and is based on CONSENT. That, in turn would put a huge limit on the power of the federal government to coerce people and to screw them over. After all, they could always leave if it got too bad. THAT is what they fought a war to try to prevent. They wanted to convert the union from one that was voluntary and based on consent to one that is coerced and is based on force, threats and violence. Once the abusive relationship has been established, they are then free to squeeze as much cash out of everyone as they like and/or to trample on others as much as they like.