FAQ for newbies who see pure @safe nothrow @nogc

[matovitch via Digitalmars-d]

On Thursday, 29 January 2015 at 10:34:37 UTC, matovitch wrote:
> On Wednesday, 28 January 2015 at 22:32:55 UTC, Jonathan Marler 
> wrote:
>>
>> Why don't we make all the function attributes keywords?
>> -----------------------------------------------------------
>
> As a newbie, I would have asked the reversed question :
>
> Why don't we make all the function attributes attributes?

To be clear, what are the avantages of keywords vs attributes ? 
Why should the most used function attributes be keywords ?