I wonder why this kind of screws are not more popular? Is it really that much harder to produce them or there is some other reason for not being used everywhere? You can use them either with flathead or Phillips head screwdriver, looks like win-win solution?
Robertson’s efficient manufacturing technique using cold forming for the screw’s head is what made the idea a commercial success, so it looks like Canadian popularized it, even though it was patented by US earlier but not commercially manufactured.