I posted this at this official forums.
It's Konami's and Sony's fault on this one.
It's Sony's fault because since they aren't killing off PS2, Konami can still release DDR on PS2.
It's Konami's fault because they see no point in bringing DDR to PS3. They brought DDR to one console since the previous one was killed off so early. They brought DDR to another console to appeal to its audience. With PS3, until the DDR fans from PS2 jump to PS3, Konami sees no reason to bring it to PS3. There's not much with the DDR graphics they could do (it doesn't require fancy graphics). Konami never comes close to filling a DVD with music, so blu-ray isn't helpful (Konami won't jam the disc with songs since they rather stick to a small amount and save songs for other versions). Konami just doesn't believe in actual downloadable music. On Xbox 360, they sell unlock keys to 10 songs each version. Konami also just doesn't see the PS3 market as being very big for DDR.
There was once a thread where a Konami rep or something mentioned whether people would like a DDR on PS3, and the majority said no, because many DDR fans are on PS2 and do not want to make the investment into PS3 and DDR. The other issue is that Konami does not have enough resources to make a PS3 specific version. Their Hawaii Studio makes DDR on 360. KCES makes DDR on Nintendo platforms. KCET makes DDR on PS2. Since Konami has greatly downsized their gaming development (which explains why their output has greatly dropped this gen and why some games like Contra 4 and SH: Homecoming were outsourced to western teams), they just don't have enough staff to also make DDR on PS3, unless they dump PS2.
What Konami has done over the years is:
-They made their Xbox DDR online focused, to cater to Xbox fans. The reason 360 sees DDR is because MS killed off the original Xbox and Konami had no choice but to move to 360.
-They make DDR on Nintendo platforms to appeal to Nintendo fans. The first one featured Mario (something Nintendo fans love), and the Hottest Party series is there to appeal to casuals on Wii (the Wii market basically, by having motion controls.
-The PS DDR games tend to be the more arcade oriented ones. Their arcade engine is still PS2, and while PS3 has PSN, Konami can still make DDR online on PS3.
I'd love to see DDR on PS3 more than anything, but in many ways I do understand why Konami just hasn't switched it to PS3. Until PS2 is dead, Konami is sticking to PS2 for DDR.
