its all depends on sort of deployment, in case of single

box hosting sql and biztalk services then absolutely no

need of active directory which is mostly happens in

development environments, but AD importance coming in to

the picture in enterprise deployments where you have

biztalk group , sql on separate boxes, more important when

you want to have cluster for high availability and

performance scalability. Because the service user accounts

and service group credentials are used across the network

and group of computers and which is maintained in common

repository called AD on windows platform.