The rule of law is not a tool of oppression; it's a check on the people with power and guns.
The revolutionaries do not have the power. So throwing away the legal system is far, far more likely to just lead to an unchecked re-entrenchment of whoever is in charge, not a new system.
If things are truly, truly catastrophic, maybe that's a risk you're willing to take. But since the average American is not, in fact, dying in the streets, most really want to continue living their lives in relative prosperity and relative freedom.