How to copy backup files to remote share in SQL Server Agent job without AD/domain accounts involvement?
To answer the specific question of why it is failing is that the service account on your server does not have the correct permissions to access the share.  

I have an environment where I have 2 servers not on a domain.  Using SQL Server Agent proxies is the way I solved this.  

I have a special account I use for the 2 machines (Your accounts with the same name and password) which I had to add to the instance level credentials (under security in SSMS Object explorer) (see MSDN article "Create a Credential" )  and add an agent proxy under the Operating System (CmdExec) .   

Once those are created you can select the account to run as (the name you gave your proxy) and it will work.  However this is on 2008 and I have not played with the 2012 agent that much.
Should still work the same though.

You would then use your robocopy line "robocopy d:\SQLBACKUP  \10.195.xx.yyy\backup /S /purge /MAXAGE:7 /MT:1 /Z" as your command (I use xcopy but it works the same).