Royal Warrants were first granted by 17th century sovereigns who needed someone to do the real soldiering whilst their noble offspring waved their steel phallic symbols in the air - sorry! - provided inspirational leadership. (Phew!)
Starting with ship's officers, the system extended to gunners and sappers in the field. In short, anyone who knew a bit about admin, logistics, tactics, training etc., but didn't have the brass or the breeding to command troops, was made a Warrant Officer. The system hasn't changed much. Yer bog standard WO2 probably packs more military experience into his little finger (pinky, you Yanks) than the average 2Lt who theoretically commands a platoon.
The strength of the system is that - in an infantry battalion at least - the WOs are the administration managers at Company and Battalion level. Their off-duty authority extends to the Warrant Officers' and Sergeants' Mess ("WOs and Joes"), of which the Regimental Sergeant Major (RSM) is the head. Some of these magnificent warriors go out with a whimper rather than a bang, by accepting Quartermaster (QM) commissions. They never get beyond Major usually, because they can't stand in the way of the bright young mainstream commissioned officers. All they can do is stand in a corner of the Officers' Mess and shake their avuncular heads at the antics of the young 'uns. The backbone of the army.