Yes but the PS3 supports AACS as part of the Blu-ray specifications.
DVD players operate according to the DVD-Video specifications and there's no simple way of adding in AACS support.
It's far easier just to go the whole way and produce a Blu-ray player that supports the lot than try to re-engineer the existing DVD technology.
Even if it were possible the main barrier in my mind would be the AACS licensing costs as there's no economic incentive to licence AACS for a standalone DVD player.
If a company is licensing AACS then they'll want to produce a Blu-ray player instead of limiting their investment and it's more likely in my mind that dedicated DVD players will eventually disappear altogether (presumably when Blu-ray players become cheap budget items).
At the moment streaming media players don't need to support AACS as part of their function and it's therefore in the interests of their manufacturers to avoid AACS licensing fees.
It's a bit of a 'Catch 22' situation in that the AACS people want to make money from licensing their product and the media streaming manufacturers have no need for AACS so won't pay to support it.
I can see it being quite likely that this situation will persist for a while yet as the media producers seem entirely focused on short term profits and appear incapable of stemming their immediate greed even if it would close a significant loophole.
Let's hope that this remains the case.