I'd still have an auto increment field in every table, but you can have another field you use as an index.
For example in my users table I have an auto incrementing id field, but I do not use it, I have another index userid.
On a side note, if you have an auto increment primary key field that is named other than id, this line needs to
be placed in model like this:

<?php namespace App;

use Illuminate\Auth\Authenticatable;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Auth\Passwords\CanResetPassword;
use Illuminate\Contracts\Auth\Authenticatable as AuthenticatableContract;
use Illuminate\Contracts\Auth\CanResetPassword as CanResetPasswordContract;

class Powner extends Model implements AuthenticatableContract, CanResetPasswordContract {

	use Authenticatable, CanResetPassword;
    protected $table = 'powners';
    protected $primaryKey = 'ownerid';   //THIS LINE
    protected $fillable = [
        'ownerid',
        'oname',
        'ostreet',
        'odate',
        'ocheck'
   ];
        public $timestamps = [];
}   

Why you have an auto_increment field if you don't use it?

Something I was taught that it's always a good idea to have such a field in SQL Server and MySQL.