Irregular common emitter amplifier design
The &quot;simple&quot; two-resistor bias circuit might be used where every component added to the parts list has a cost, or space is strictly limited. Comparing the simple-bias circuit against the 4-resistor bias circuit:
Advantages of simple circuit:

SIMPLE DC bias with small parts-count
shunt feedback resistor improves linearity
less likely to oscillate if reactive source and load is present

Disadvantages of simple circuit:

less stable DC operating point for different transistors
DC bias is less temperature-stable
low input impedance due to shunt feedback
shunt feedback reduces maximum gain possible. (for RF, may be a good thing)
shunt feedback reduces output-to-input isolation