Casette tapes are still manufacturer by National Audio Company Inc.
The NAC factory is located a few blocks from my home in downtown Springfield, MO. Really great folks. I know a few musicians in town that work there and seem to really enjoy it.
In addition to blank media they also produce/duplicate projects you want printed to tape/CD/whatever. About five years ago a local band enlisted me to help them record/mix their next album. With NAC right here in town, they released the album on cassette with an accompanying digital download. We figured a lot of the people that would be buying the album were just as likely to listen to a cassette as a CD if all they wanted was the MP3 copy anyway, so why not have the added novelty of the tape. NAC's pricing was pretty fantastic, so it was cheap enough the band could sell the tape/digital download version for $5 each and still come out in the black. The tape duplication even included jewel cases and full color inserts.
So while I'm not sure how many people listened to their hard copies, I will say the NAC tapes sound pretty dang good.