Longer functions are much more prone to causing errors, and errors that are harder to find. It is honestly much better to have functions that do one thing and one thing only. Might not always be possible, but it is always the best way to code.
I think “doing one thing” and “getting called one time” are getting confused.
GetData()
FormatData()
UploadData()
Those could do one thing but could be called at several points within a larger program, which i think you are fine with. Or they could only be called once in which case i think you are saying it might make sense to just inline them.
I don't necessarily agree with "one thing only". At least, for things that start simple and grow as needed, I split things into functions either to not have to copy and paste the same code, or for readability/structure purpose. But not out of principle and always, until I can't divide any further. I can still split things out into functions later, should I need it, but doing it "just in case" and then not even having a use for it doesn't save me time and just adds overhead.
Though it also depends on whether I'm doing something familiar or something new, if I'm doing something new I might split things up more to help me conceptualize the problem. But when I'm just making a quick CLI tool, I might put it all in main first and only split it up as needed.
