I am sure I saw a posting a while back (on some board) that RC announced that the first run was completely sold out. Whoever (Hobby Shops, Retailers, etc...) ordered them would get them but if anyone else tried to order they would be informed that they were sold out.
And a second run would be based on additional demand. If it wasn't there, they would not run any more (hence "discontinued").
Maybe Tower waited to long to put their order in and are out of luck in getting any. And on their website they put "discontinued" as, in their case, unless there is a second run, they are, in all fact, really "discontinued".
James