Exactly what we are all saying.
Nope, 0% confused. You're massively confused if you're bringing analog into a compression discussion (compression in analog is just passing the frequencies through a bandpass filter basically), and think that reducing multiple gigabits worth of data into 30 megs is not lossy compression.
There are encoding techniques that can save bandwidth with little to no quality loss, but nowhere near that much.
Just like with music, the bitrate and size determines the quality. MP3 will always have loss, FLAC can encode lossless and save room vs PCM but is far bigger.
Rather than "thinking" everyone else here is wrong, just do some googling. Or watch a blu ray then the same thing streaming, doesn't get much simpler than that to see the proof.