Why set casts in model when its date in migration ?

In my migration :

        Schema::create('news', function (Blueprint $table) {
            $table->id();
            // ...
            $table->date('published');
            $table->timestamps();
        });

In app/Nova/News.php

    public function fields(NovaRequest $request)
    {
        return [
            ID::make()->sortable(),

            / ...

            Date::make('Published Date', 'published')
            ->sortable()
            ->rules('required'),
        ];
    }

Date field must cast to 'date' in Eloquent model.

I had to do in app/Models/News.php to make it work.

    protected $casts = [
        'published' => 'date' # datetime:Y-m-d
    ];

Why do I have to do this extra casts when in my migration its clearly date type and and in Nova I'm setting it to Date::make ?