Everything about this format is analog on purpose, and that’s not nostalgia for its own sake. It needs no software update, no electricity, no connection to any grid at all. Wind it by hand, and it plays, regardless of what year it is or what’s still supported.
The part that matters more than any of that, though, is that each piece is finite. It cannot be copied. A cassette made as a piece of art, or as someone’s memoir, a wedding, a child, a life, exists exactly once. It can’t be duplicated, pirated, uploaded, or shared the way anything digital inevitably is, sooner or later, whether you want it to be or not.
That makes it a small, fixed, contained little ecosystem of its own, frozen at the moment it was made. A time capsule, quite literally, not as a metaphor.