In Hollywood's defense, I'd imagine this is simply the IP version of the 555-XXX convention for phone numbers: so fools won't simply type whatever IP address they see on screen, thinking they've just Hacked the Gibson.

498,438,559,990KG? What does that convert to in tubes?

You plonks just sparkle. We shine.

Oh, and to E.T.: I've got your ouch right here.