1. Data doesn't come on the HDD. It needs to be stamped on something first, which once again raises the issue of storage capacity.
2. Again, consoles were using games on DVDs long before the PC did. PC games on DVD have only become standard over the last couple of years. Devs were still shipping games on multiple CDs. The problem being proliferation of said drives. For consoles, the drive is guaranteed in the box, so there's no reason for console devs to wait. They can start exploiting the extra space of BD now.
3. How the game looks means nothing. Have you seen all the levels of Crysis and Resistance? Have you gone through and taken inventory of the scenery in each game? 40 levels with 300MB of unique data each amounts to 12GB of just level data. But hey, what do the actual devs of the game know? I mean, they must not have a good reason for needing over 20GB of space, right? They certainly weren't able to fit those R&C games on a single DVD in the past, so it must be indicative of their inability to shrink a game down....
Sorry for the sarcasm, but I find the attitude in this thread to be bordering on the point of ignorance. If you build it, they will come. Just b/c there hasn't been a need before, doesn't mean there won't be in the future. Just because you can't think of a good way to use that extra space, doesn't mean some dev won't come along and make that extra space almost a necessity. For a technical forum, sometimes we can be extremely resistant to change. PEACE.