And how often would you want to connect an external drive at the same time you need to connect the laptop for charging? I'll grant that only having a single multipurpose connection point (like the new 12" MacBook) could be a bit of a bother in situations like that, but I can't see it being an obstacle.
It is a huge obstacle. Choose one:
- Leave you Time Machine Backup external hard drive permanently plugged, as Apple recomends
- Have your iPhone plugged to charge, or to develop
... or, you know, charging your laptop
Saying "get an USB hub" is not a valid answer, as it just means "get more ports, but buy them apart"