Actually, you would miss them, cause you used them every time you applied the brakes...

As centering screws, I agree they're stupidly redundant, because DPs are easily centred via the handy lever fixed to the main pivot bolt that's formed by the third bit of ally that's there to hang the side pivot from. As you say, centering is dead easy - I just put a thumb under the end of each caliper to hold them open against the cable and turn the brake around its mounting bolt, using my fingers to ensure most of the effort gets there.

But the bottom of the screw forms a fulcrum point where the high-leverage arm adds force to the centrally-pivoted one. I'd be interested to feel the difference eliminating this fulcrum would make... I suppose the brake would still kinda work.

Actually, I guess the adjustment might serve an aesthetic purpose; to allow the arms to line up across the top given different rim widths and pad thickness maybe.

I like the grub screws. You could fill the screw head recess with melted wax to tidy it up if you like... wax weighs less than steel ; )

Also, if you can't get any purchase on that screw with a slot screwdriver jammed in, I'd just disassemble the caliper and go from underneath with pliers until the screw head's exposed.