As far as we know, just out of stock, which is common with Home Automation Devices these days.
@jkp gave you a link in post 17 above to a company which does usually have it in stock.
I’ve never bought anything from that particular company, but I have purchased several times from zwaveproducts.com and they also show it as being in stock at the time of this posting.
But you never know these days, smartthings doesn’t generally make announcements in advance about hardware decisions. 