Hi,
I have no idea why the APU's are not released yet to the general public.
Mainstream vendors like HP have already released desktop computers using the APU's.
Here is a link to a home system from HP with a an AMD A12-9800 AM4 socket processor.
https://support.hp.com/us-en/document/c05281246
And here is a link to a system configurator to a business grade HP system. You can choose a number of AMD APU options. This HP Elite Desk 705 comes in three different case styles. A Mini-PC, a small form factor desktop and a Micro Tower
http://www8.hp.com/us/en/products/desktops/product-detail.html?oid=10669598
In the USA you can configure it with all sorts of storage and RAM options. In other parts of the world you don't have as many options....basically HP preconfigure a couple of different options and thats all the choice you have.
Regards,
John.