When do you need to build for differient platforms?

[Uncanny_Valley]

I remember reading about this in a post a long time ago, but can't find it. Do you always need to build seperate versions for windows, linux and osx?

For example, do I need seperate versions for my Tavern Redone mod? As it only contains world data override,

[Ralzar]

All my mods are only built for windows. And I've had no one ask for a linux/mac version so I assume they've just worked for those systems as well.
So I'm not sure exactly when you need to build linux/os versions.