"All signals with content entirely below the Nyquist frequency (half the sampling rate) are captured perfectly and completely by sampling; an infinite sampling rate is not required. Sampling doesn't affect frequency response or phase. The analog signal can be reconstructed losslessly, smoothly, and with the exact timing of the original analog signal."
Analog reproduction is far less complex and easier to explain in pictures to an unknown entity that might find it. Figure that they'll need to build what effectively amounts to a record player to play the thing back. In addition there was no digital technology of the time with a large enough capacity to store what we sent, or that was durable enough to deal with an unknown time in space.
Quality of the reproduction is not a consideration.
"All signals with content entirely below the Nyquist frequency (half the sampling rate) are captured perfectly and completely by sampling; an infinite sampling rate is not required. Sampling doesn't affect frequency response or phase. The analog signal can be reconstructed losslessly, smoothly, and with the exact timing of the original analog signal."