Part of it is nostalgia, and I have a stereo that plays cassettes, but more than that it's just cool. It doesn't have to be convenient because it's art. There's no utilitarian reason anyone should feel connected to an album for anything besides the music, but I (and others) do.
Also they're cheap to make and sell.
Thank you! I don't appreciate being called "silly" over listening to cassettes either, and it makes people who strictly listen to vinyl come off as elitist and angry. I don't criticize that, so why criticize this? I have a right to appreciate tapes if I want to, quit getting fucking weird about it and let people be.