Bandwidth is not the only consideration. Apple sells MacBook air's with a single 64GB 'disk'. On such a system, users will notice a difference if you manage to save 'a couple hundred megs' a few times.
Quick note: they do not sell 64Gb MBAs anymore. I don't think they have since last year.
Uh, yes they do. The options are 64/128 for the 11", and 128/256 for the 13".
Even if that were true, the price of Apple's early adoption is that they have to support it for four years. (Just like they supported 32-bit x86 for years even though they only used it for a short time.)