Request in laravel doesn't form slug field?

Question

Laravel

in the model

public function setSlugAttribute($value){
        $this->attributes['slug'] = Str::slug($this->title,"-");
    }

In the controller

public function store(Request $request)
    { 
        dd($request->all());
    }

At the exit:

array:5 [▼
  "title" => "Second"
  "published" => "1"
  "slug" => null
  "parent_id" => "0"
]

The question is why slug = null? Although if you register saving in the database in the model,
Category::create($request->all());
then everything is fine. The slug is formed as it should.

Answer 1

The mutator only works when you set a model property and Request has nothing to do with it.

Answer 2

Request field in laravel is not formed by mutators?

No.