Back when we had cassettes everybody was excited to buy albums and play them on their walkman. When CDs became popular during the 1998-2000 era, it was the industry at its prime and everyone bought their CDs to play them on their awesome portable CD players. It clearly went downhill ever since
MP3 players and iPods had become popular.
I don't think P2P sharing is the main problem since it was already there when we used to burn songs into CDs, and the industry was just fine. Nowadays, It's just easier to download music illegally and just upload them to your player than downloading iTunes and then purchasing MP3s. Buying CDs is not practical at all. Where would I use it?

If I use the stereo, I just plug the MP3 player with the audio output, If I'm in the car I just use the mp3-to-cassette adapter since it's much better than having the CD player and you'd have to deal with the scratched CDs and their skipping. CDs are just useless and buying MP3s is not practical either.
What do you think?