Escape and f-keys are used to send commands to the computer, not to enter text. Apple feels that this is better achieved with touch, gestures, and the mouse, so they've removed the temptation for developers to fall into old bad habits. See also: the removal of arrow keys on the original Mac.
And have you ever tried to use a terminal (editor) on remote over a connection with high latency? Awful.
2. Gotta agree with easytiger. I work all the time from 3G tether connection. Mosh makes it a breeze.
That's why ed doesn't prompt. (ed is the standard text editor.)
Or you could use nano.
Applications that have terminal UIs tend to be significantly more well behaved than those that don't, this isn't always the case it's just a trend I've noticed.
The bar is programmable, so I would expect that applications like iTerm will write in support for it and they probably would include an ESC key on the bar. It would be nice if Apple had thought of this and Terminal.app already did that. Maybe they didn't think about that, but my guess is that they work mostly in Xcode.
Then there is the suggestion from someone else in the comments to remap the Caps Lock key to ESC which might be something I try even though I pretty much use full keyboards. The ESC key on home row might be a great idea.