Why transmission line 11KV , 33KV, 66KV not in 10KV 20KV?

 Why transmission line 11KV , 33KV, 66KV not in 10KV 20KV?

if we consider 11kV, then the voltage should come 11111V
but the case is we get 11000V.
Think on it guys, 11kV has nothing to do with form factor. 

 Form factor is the ratio of RMS/Average value which 
equals 1.11

If the Form factor 1.11 then the voltage waveform is pure sine wave.

Any AC voltage will have a form factor irrespective of the voltage level. Variation in the form factor value will tell how good the sine wave is. 

if a 440V AC sine wave with form factor 1.11 is stepped down or stepped up to any value, still that waveform have a form factor of 1.11

So form factor is the quality of the sine wave. Its not a deciding factor on how much the voltage should be.

§  The miss concept is Line voltage is in multiple of 11 due to Form Factor.  The form factor of an alternating current waveform (signal) is the ratio of the RMS (Root Mean Square) value to the average value (mathematical mean of absolute values of all points on the waveform). In case of a sinusoidal wave, the form factor is 1.11.

§  The Main reason is something historical. In olden days when the electricity becomes popular, the people had a misconception that in the transmission line there would be a voltage loss of around 10%. So in order to get 100 at the load point they started sending 110 from supply side. This is the reason. It has nothing to do with form factor (1.11).

§  Nowadays that thought has changed and we are using 400 V instead of 440 V, or 230 V instead of 220 V.

§  Also alternators are now available with terminal voltages from 10.5 kV to 15.5 kV so generation in multiples of 11 does not arise.  Now a days when, we have voltage correction systems, power factor improving capacitors, which can boost/correct voltage to desired level, we are using the exact voltages like 400KV in spite of 444KV