The new music is fine, everything is on youtube.... for now! ... but the older songs are disappearing.
Years ago, we had a bunch of "mp3 sites" (websites where you could download pirated mp3s), that disappeared, a huge local torrent tracker, focusing also on local stuff, that lost most of the data in the OVH datacenter fire and slowly died, and some stuff was put on youtube 15 years ago, and then got copyright claimed 5 years ago, and was removed. The music groups don't exist anymore, so the CDs aren't publushed anymore, second hand shops are very rare and cater mostly to LPs and tourists, and the groups stopped existing before they could sign deals with the publisher for streaming services.
So yeah, it's not just "those semi-personal photos taken on a party and kept by maybe one or two people", but also pop-music that used to be on the radio all the time in late 80s, early 90s, and is just..gone!
I'm sure that there are data hoarders somewhere, that have mp3s of all those songs somewhere, but unless we get some p2p type of service like gnutella/ed2k/kazaa working again, I won't be able to find them anymore.