Why did the Death Star Plans have to be Physically Carried?

As the title, how can the galaxy have instantaneous wireless 3D video communication across arbitrary distance, but the Death Star plans had to be carried in one copy by the space travel equivalent of IPoAC? They seem important enough that the Rebels might be willing to send them to a bunch of different ships in different areas of the galaxy (remember, they can send data instantaneously over any distance) and then immediately have them make the jump to hyperspace with the destination somewhere else, to evade Imperial interception (assuming the signal could be intercepted and traced in the first place).

I do realize that the real answer is that the writers had no idea that FTL communication opens up such a huge can of worms, I'm just interested if it was ever explained in-universe.