Hold on there sir.
That was just one of many usage scenarios where it would be more favorable to have at LEAST two ports.
For example, my current set up is that when I get home, I connect my Macbook to an external, 19" monitor. I close the lid, and plug in my USB Mouse/Keyboard and plug in the power. That way, I have more screen space.
I could buy a bluetooth mouse/keyboard... But then, it doesn't stop there anyways. Then I plug in my USB 3.0 HDD and do backups, for example.
Can't plug in the MBA when it's backing up? Oh crap.
Can't use my mouse while using a flash drive?
Cloud transfer isn't easy especially across eco-systems. Nor do I have a cloud service common between my School computers and my home computer.
There are many reasons that you'd want more than one port. I don't think it's fair to say that having one port and only one port is advantageous or even feasible.