Because size matters!
Sony can't build a walkman with tubes inside, same goes for 99% of mass market audio gears out there. Imagine if Sony had to build a 5-channel HT receiver with tubes, it will take up quite a bit of floor space.
Same goes for media. Reel-to-reel, LP, cassette, CD, MP3, and who knows what's coming next. Each generation degrades the sound, but 99% of people out there don't care because they can carry more garbage with them everywhere they go.
Sony can't build a walkman with tubes inside, same goes for 99% of mass market audio gears out there. Imagine if Sony had to build a 5-channel HT receiver with tubes, it will take up quite a bit of floor space.
Same goes for media. Reel-to-reel, LP, cassette, CD, MP3, and who knows what's coming next. Each generation degrades the sound, but 99% of people out there don't care because they can carry more garbage with them everywhere they go.