There already exist USB interfaces that allow you to connect arcade controls. And there are also other USB interfaces that allow you to connect one type of original game controllers or another type of controllers. In some cases these interfaces also only allow to connect a controller for one player.
The key feature of the GamepadBlock is that it supports a whole range of controller types at the same time. It, therefore, combines several of the individually available adapters within one device. And since the GamepadBlock is USB HID-compliant, it can be used on Windows, MacOS, and Linux including system-on-chip platforms like the Raspberry Pi or Odroid. For all gaming consoles that are supported two gamepads can be connected. And you can even switch between the controller types via a virtual COM port.