Why some function are class-less?

[Suliman via Digitalmars-d-learn]

On Thursday, 17 November 2016 at 17:45:31 UTC, Stefan Koch wrote:
> On Thursday, 17 November 2016 at 17:42:44 UTC, Suliman wrote:
>> On Thursday, 17 November 2016 at 16:46:37 UTC, Steven 
>> Schveighoffer wrote:
>>> On 11/17/16 11:28 AM, Suliman wrote:
>>>> [...]
>>>
>>> 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)?
>
> for example writeln.
> You would not want to create a stdio object just to call 
> writeln.

Ok, but when the logger class may be more helpful that function 
usage?