Why some function are class-less?

[Suliman via Digitalmars-d-learn]

There is some functions that can be called without creation of 
class.
For example: http://vibed.org/api/vibe.core.log/
As I understand I can create write log in two way. First create 
instance of Logger, second simply call function.

Why it's done so? Just as shortcut? But is I create class it's 
look very poor http://vibed.org/api/vibe.core.log/FileLogger and 
I have only one needed method: ` put 	Writes part of a log line 
message. `