Back in the old days of analog audio, splitting a signal was no big deal. Just use a ‘Y’ adaptor. Or if you’re punching down wires, just punch another pair on top of the first. Of course, each signal will be 3 dB lower than the original, but that’s not a worry. That’s because the wavelength of audio is miles long (quarter-wavelength at 20 kHz is more than 2 miles!).
While adding wires might change the impedance, it didn’t matter. You couldn’t go far enough for it to matter. But when it came to video, it was a different story. The signal is a lot higher frequency, so the wavelength is shorter. While you might get by with a BNC ‘T’, this would cause a mismatch on the two splits and could result in some reflected signals. Read more