Reasons to use a voltage divider and regulator?
In general, you have got three different opportunities to reduce your battery voltage from 3V to 2V. Each opportunity has got its own advantages and disadvantages and should (must) be used for different applications:


Voltage divider:
Voltage divider are used for applications which don't need any current but a common reference voltage. You can't drive a huge current because this would change your divide proportion. Mention that V_out depends on V_in. So if your battery voltage goes down, your reference voltage goes down too.


Typically applications: OP gain resistors, Voltage for feedback inputs


Reference diode:
Reference diodes are used for applications which don't need any current but a very exact reference voltage. In this case your reference voltage doesn't depend on V_in.


Typically application: ADC reference, OP circuits


Voltage regulator:
Voltage regulators are used for applications which need more or less load current. In this case your voltage doesn't depend on V_in. There are two different types of voltage regulators. On the one hand you can easily use a linear regulator or on the other hand you can use a clocked buck down regulator for high efficiency.


Typically applications: Supply voltage for circuit parts

Hope this help you!