There several reasons for using a lower windshield when off roading. You´ll get a better airflow to your body and this will maintain your body at a good temperature and allow you to perform better driving this heavy monster.
Your field of view will be improved since the windshield is smaller and in case it gets dirty it won´t disturb your view.
You´ll get the aggressive look of rally bikes, and that sporty feeling you´re driving a race machine!