It is needed to simulate the weight and aerodynamics of the missile. If you want the simulation to be realistic then you should probably carry them.
Captive air training missiles have their role in training, yes, however are CATMs
necessary in DACT?
For example, if you had an aircraft doing DACT, does the actual notional weapons loadout of the aircraft have to be physically represented by an equal number of captive training missiles?
I've watched a number of DACT videos in the past, and from what I've seen it seems to be rare that for anymore than an ACMI pod and one or two CATMs (if that) are being observed carried for any one mission.
Which takes me back to the previous point -- is a training missile actually
necessary to simulate an aircraft carrying said missile types, for purposes of DACT?
I can't help but feel like if it was necessary, we'd be seeing a lot more pictures of aircraft during DACT exercises loaded with more missiles.