Urban militias are not army units

[Dark_Magician]

Well this is just it - city guards are employed by the relevant City Councils to do following:

1) Keep law and order in the cities (+ loyalty inside city).
2) Man city defences (towers, walls) and equipment (oil boils).

They are paid by the citizens and not by the central budget, at least nowhere in developed societies where cities are following Magdeburg (sp?) code or Lubeck law! This means the costs of the town militia to the Crown (especially in the cities under their own jurisdiction and self-governement) is zero and these units are not to be taken out outside their city. To do it - be you king or senior - you'd have to take the city first.. so you would then be in possession of their bodies.

EDIT:

In simple terms, militias are better at keeping law and order than the army. They are locals and familiar with the city, they know bad spots and they don't incite hatred. They know the towers and walls stuff too.

On the other hand they aren't trained to march in lines and sing songs as regulars are.