If stuff is designed for big servers that run Linux, it's easier to get it to run on a desktop PC if the PC runs Linux too because then it's the same thing except much less powerful.
Code and snippets to analyze data work well when you can send chunks of it to multiple servers (think analyzing the effect of weather patterns).
Since a lot of that stuff is running on Linux (similar to cloud computing) it makes sense that people that write function/scripts/utilities would already be comfortable in that environment and use it as their daily driver.
They certainly do, at least to an extent. In many fields where you have to work with a lot of data people will use R or Python to handle/transform/perform calculations.
If you compare with excel or similar. They do not write excel the program. But there is a lot of tinkering with algorithms and functions to get the wanted results.