TL:DR; It was cheaper and they figured if it didn’t work you could flip it over and try again. So it’s mildly inconvenient to save a few cents on manufacturing each connector and to limited the number is conductors to 4, something it turns out was a bad idea anyway because newer USB standards use more than 4 conductors.
That is one way to deal with the problem, but it comes with its own tradeoffs. In particular that reversible type-a is incredibly fragile due to how thin the plastic supporting the pins needs to be to fit within the housing. They could make the plug bigger of course, but now you’re adding more cost and decreasing the areas the plug can potentially be used in due to its increased size. Conductor routing also becomes more problematic as you need to cross conductors to opposite sides now. Additionally while that cuts down on conductors needed in the actual cable, you still end up needing 8 pins/conductors in the plug, one set of 4 on each side of the plug.
TL:DR; It was cheaper and they figured if it didn’t work you could flip it over and try again. So it’s mildly inconvenient to save a few cents on manufacturing each connector and to limited the number is conductors to 4, something it turns out was a bad idea anyway because newer USB standards use more than 4 conductors.
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That is one way to deal with the problem, but it comes with its own tradeoffs. In particular that reversible type-a is incredibly fragile due to how thin the plastic supporting the pins needs to be to fit within the housing. They could make the plug bigger of course, but now you’re adding more cost and decreasing the areas the plug can potentially be used in due to its increased size. Conductor routing also becomes more problematic as you need to cross conductors to opposite sides now. Additionally while that cuts down on conductors needed in the actual cable, you still end up needing 8 pins/conductors in the plug, one set of 4 on each side of the plug.