I think, given this economy, they wanted to keep the price as low as possible and allow the customers to make decisions from there. I say it was a good move.
Heck, you can buy the 8GB model, only buy games on disc, and probably never run out of room for saves for the console's lifetime. If you really play a TON of games and have a lot of save files, you may have to look into an SD card down the line, and I will admit I have no clue when it comes to those things as to pricing. But, I think for a lot of "light" gamers, they can buy the console "as is," buy games only from brick and mortar stores, and never have to worry about an external HDD.
Me? I got a 1TB external HDD right away, because I think this is going to be my first all-digital console (aside from Nintendoland, of course). As Bankai was saying, running games digitally does save on laser stress (for all the people who never had a laser problem, you can easily find someone who did have a laser problem, so on and so forth), and it's just easier than having to open the tray and switch out games all the time (I switch between games a lot... maybe too much lol).