Excuse my ignorance!

[alpinerabbit]

Because it would be unpleasant, and in sweaty conditions impossible, to keep a grip on the plain metal bars for extended amounts of time (?)

[BleeckerSt_Girl]

And the metal bars would be FREEZING in the winter....even with gloves on.

[alpinerabbit]

yup, actually in freezing/wet conditions your gloves would get stuck

I saw an old track bike once - wood rims, wood handle thingies on the bar ends - you'd just hold there.

Man, I shoulda bought it.

[Eden]

Handlebar "tape" is not exactly what the name implies too - while some is sticky on the back to help it to stay in place, its called tape more because of its shape (like a "tape measure") more than anything else. Its a roll of material, traditionally cork or fabric, though now often made of foam rubber, that you put on your handlebars to provide padding and a non-slip surface. Road bikers use it for the same reason you put rubber grips on the ends of a flat bar.

[jobob]

Plus it looks nice.

[SadieKate]

And now the cables run under the tape, so it helps keep them nice and tidy out of the way.

[Jiffer]

And you can put gel like stuff on the handlebars, underneath the tape to make the handlebars extra comfy.

But I think it's mostly so you can have PINK handlebars!!! HA HA!!!