How to fix it Call to a member function diffForHumans() on string in laravel 5.3

Why when I use query builder instead there is an error on the function diffForHumans (), but if I use ELoquent ROM but no error there is a way to overcome it? (How can i fix it) thank you

diffForHumans()

this is ArticlesController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Article;
use Carbon\Carbon;
use Auth;
use DB;

class ArticlesController extends Controller
{

    public function index()
    {
        $articles =DB::table('articles')->get();
        $articles = ['articles'=>$articles];
        return view('articles.index',$articles);
    }
}

this is model Article.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use Carbon\Carbon;
use Illuminate\Database\Eloquent\SoftDeletes;

class Article extends Model
{
    //
    use SoftDeletes ;

    protected $fillable = [
        'user_id','content','live','post_on',
    ];

    protected $dates =[
        'post_on','deleted_at','created_at','updated_at',
    ];

    public function setLiveAttribute($value)
    {
        $this->attributes['live'] = (boolean)($value);
    }

    public function getShortContentAttribute()
    {
        return substr($this->content,0,random_int(60,150))."...";
    }

    public function setPostOnAttribute($value)
    {
        $this->attributes['post_on'] = Carbon::parse($value);
    }

    public function setCreatedAtAttribute($value)
    {
        $this->attributes['post_on'] = Carbon::parse($value);
    }



}

and that is my code, how i can fix it? thank you