Actually, if you work on pretty much any sort of machinery other than late model cars, you'll need common screw drivers of a great many sizes.
The most obvious example is small-arms work, where the screws are all slotted, and one must have screw drivers which fit the screw slots exactly, to turn the screws without damaging them.
In gun work, particularly on older guns, its common to carefully grind a screw driver to fit the screw slots on a particular gun......the old British double shotguns are notorious for this, as the slots were narrower than American practice, and of no specific width, often as much as .005 or so different amongst the screws on any one gun. I have some sixty-odd...more or less.... probably more, actually, I really don't know just how many.....screw drivers, which I've accumulated over the years, and still have to modify the tips as needed for this or that task.
Cars and trucks of the pre-war era had nothing but slotted screws, many in the electricals, with soft brass screw heads. Chevrolet cars and truck engines were known as 'stovebolts' from the many 'stovebolt' slotted-head screws used on the oil pan and sideplates.
Screw drivers which fit the screw heads correctly, and had a suitable shank and handle length were essential, if one was to make reasonable time on one's work. One would need 'stubby' screw drivers for some tight locations, long-shank ones for others, and screw driver tips for socket ratchets/breaker bars for some applications where significant torque was required turn the screws.
The Phillips and Reed-Prince screws weren't commonly used until the 1940's. These, of course, were faster or more convenient to drive in production, as were the 'clutch-head' screws used by General Motors or the less common Canadian pattern 'Robertson' screws.
If you are so fortunate as to be able to work primarily on equipment which has Allen head or Bristol spline screws, or the more modern 'torx', you are indeed lucky......... : )
cheers
Carla