alt Hacker NewsPhillips Heads: The design is often criticized for its tendency to cam out at lower torque levels than other "cross head" designs. There has long been a popular belief that this was a deliberate feature of the design, to assemble aluminium aircraft without overtightening the fasteners.[15]: 85 [16] There is no good evidence for this suggestion, and the property is not mentioned in the original patents.[17]
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It has more to do with manufacturing techniques. Screw heads are stamped. A cone shape, with all sloped sides, is easier to stamp reliably. Even the famed Robertson bits from canada have a slight slope for this reason.
If I were to speculate, the point of phillips head was to just be easier to use than flat head while still being easy to manufacture 90 years ago. The better heads introduced since then have more intricate designs that require more precise manufacturing than a simple stamp
https://en.wikipedia.org/wiki/List_of_screw_drives#Phillips