Why some function are class-less?

[Suliman via Digitalmars-d-learn]

On Thursday, 17 November 2016 at 16:46:37 UTC, Steven 
Schveighoffer wrote:
> On 11/17/16 11:28 AM, Suliman wrote:
>> 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. `
>
> D does not require classes to write functions. All a class 
> member function is anyway is a function with an implied class 
> instance parameter.
>
> -Steve

Ok, but what profit? Could you give me an example (for example 
with logger)?