[TD-Linux]

I think the GP mostly answered it, but usually it's so that they are self-consistent with a set of design rules, and known to work. Every place I've done professional PCB work has had their own library.

I think this trend comes from exposure to really poor standard libraries - for example, I found Altium's libraries being especially inconsistent and weird (though it's been a few years since I've last used Altium).

I've personally found the KiCAD standard libraries to be very consistent and high quality in comparison (both the symbols and footprints), and have no problem using them on my own designs - in fact, if I have to make my own schematic symbol, I often reference the standard libraries' design rules when making it.

[dotancohen]

I see, thank you.