That's a bad analogy. It wrong because you can see what doors, cupboards and drawers are available for the public. Doors that are in-reach but that shouldn't be used by the public have signs like "restricted access" or "employees only". You can't do that with the internet. You can't see that a port is not available to you until you try it.

If you want to continue using that analogy, then you have to consider that everybody is blind and deaf, and checking to see what's locked is the only way to know if something is available.