BJT Veb matter & use of the Ic-Veb Exponential Relationship
In the enclosed figure (first diagram) it is shown how an emitter resistor RE stabilizes the operating point against uncertainties of VBE. Hence, it is common practice to assume for VBE a suitable value between 0.6 and 0.7 volts because such a relatively large VBE uncertainty results only in small Ic variations (for sufficient RE-feedback). 

The dotted line (vertical) shows how RE=0 (no feedback) would result in an unacceptable large Ic variation (uncerainty).