They don't.
Scientific calculations are always done in Celsius, where the freezing point of water is set at 0, and the boiling point at 100.
Fahrenheit is a scale that the founder set water freezing at 32 degrees because this way it would never reach 0 degrees (unless you get ridiculously below freezing).
The logic of Celsius is better and that why scientist use it.
Most scientist now use the Celsius scale.
Celsius
celsius, fahrenheit and kelvin.
The units that scientists use to measure temperature are: Celsius Fahrenheit Kelvin
Fahrenheit
Scientists generally use Celsius (or Kelvin) to measure temperature, as it is the standard unit in the scientific community. Fahrenheit is rarely used in scientific studies or publications.
The temperature scale is Fahrenheit, named for scientist Daniel Gabriel Fahrenheit.
The temperature scale is Fahrenheit (°F), named for scientist Daniel Gabriel Fahrenheit.
The scientist for whom the temperature scale is named was Daniel Gabriel Fahrenheit (1686-1736)
Daniel Fahrenheit, in 1714.
The temperature scale is Fahrenheit, named for scientist Daniel Gabriel Fahrenheit.
Named from Gabriel Daniel Fahrenheit. A scientist whom created the Fahrenheit thermometer scale. The surname means "experience"