Why there is no temperature scale tied to normal human body temperature? Fahrenheit:


  The lower defining point, 0 °F, was established as the temperature of
  a solution of brine made from equal parts of ice and salt.


Celsius:


  0 °C was defined as the freezing point of water and 100 °C was
  defined as the boiling point of water


Why hasn't anyone used human body normal temperature as 0? It would be much more logical for humans to base temperature scale on our body, not something that is outside.
Why nobody used human body normal temperature as 0?

That has been done.
See Medical Thermometry and Human Temperature at page 12:

37° Centigrade scale
29.6° Reaumur
98.6° Fahrenheit
77° Walferdin's tetracentigrade
0° of the physiological scale

Then the physiological scale is further discussed starting on page 265, which includes a drawing of a physiological scale thermometer.

physiological 0 is placed in the centre of the drama, whose acts are health, sickness, and death