We need to expend effort to keep names short, while it is easy to let them become long. 'Keep it short' is shorthand for 'do not forget to expend effort towards keeping names from becoming long'. It's easy to unthinkingly come up with 'company_people'. It takes effort to reduce it to 'employees'.
It's actually not just 'short', but 'short and simple'.
I think it's the other way around. Programmers instinctively want to keep names elegant, similar to how they structure their code. IMO they actually have to kind of step out of their comfort zone if they want to write an ugly (but clear) name.
It's actually not just 'short', but 'short and simple'.