Very true, and it's something that I'm hoping Google might correct in the future.

For example, one of the very cool demos at Google IO was where you could push a plotted route in Google Maps to your phone. It would be great if, in the background, the phone also loaded all map data along that route and at least saved it to the SD card.

Also, the new Garmin phone that runs on Android does load map data, I believe. I'm not clear on the specifics, though.