There are many fundamental difference between standing armies and/or organized militias and violent mobs in terms of scale, martial effectiveness, negotiations, treaties and post-conflict continuation.

Mobs don't win wars, they merely destroy and the rest is left to fate, often with disastrous results(see Libya as an example).

Mobs can't sit at the negotiation table

Mobs can't agree to treaties and enforce them

Mobs can't form proper functioning and recognized government.