To keep archive location for both primary and standby in shared location
It becomes a SPOF (Single Point of Failure)
It won't work across long distances -- which is what DR / Standby Sites are generally expected to be.
You would use this implementation for a Reporting environment that uses DataGuard architecture.
Agreed, I shared this information based on my experience. There may be some situations where they have more worry on the server, In such cases certainly this kind of setup will be helpful.
If DR location is not in same data center, then of course there is no concept of shared location of archives and as you said out of High availability.