Do Circumstance Bonuses Stack?

Does Cooperative Crafting (+2 circumstance bonus) stack with masterwork artisan tools (+2 circumstance bonus). If not, who would ever take Cooperative Crafting feat?

Yes, they stack.

With the exception of dodge bonuses,

most circumstance bonuses, and racial bonuses, only the
better bonus of a given type works (see Combining Magical
Effects).

They stack when the circumstances that cause the bonus are different. In the above question yes they should stack. Having qualified help and exceptional tools are different sorts of aid.

As stated circumstance bonuses stack as long as they come from different circumstances.