@thomasfuchs the key thing to understand is that the tooling to manufacture a brand new kind of connector is really expensive. It is a lot easier to point at an existing connector and say "hey can I buy a hundred thousand of those too?" than reinvent the wheel.
The Atari 2600 only supports 2KB cartridges because nobody was selling a slightly wider cartridge slot (for more address lines) at the time. Adding two more little pins was a harder problem than putting mapper chips in millions of carts