Right now, the PS3 does a good job on bluray playback and I don't need the capability in the PC. I will probably get a standalone player later this year as well.
I'm also trying to keep costs down on this build so I didn't go all out in a few other areas as well (CPU, video card, bluray, etc). I figured that I would start off with a good system for multimedia files (music, video), internet streaming (hulu, netflix), and basic gaming. If I needed more juice down the road, I could upgrade those components.
The components were just over $625 with shipping and replacing the DVD with a bluray drive would have added another $75-80 (more than 10% of the total). Since I was splurging a bit on the case and keyboard already, I decided to go easy in a few of the other areas that I would be more likely to upgrade sooner.