This architecture can be used when your organization does not value their secondary data center the same as the primary. It is a best practice to have matched or similar hardware between your primary and disaster recovery sites but that is not always possible. When costs need to be reduced it is better to have one failover server that you know can handle the work load rather than two servers which are under powered. Under powered hardware can easily become an effective outage if they cause timeouts as soon as a production work load is placed on them.
For many small to medium-sized enterprises, this might be the easiest route to sell to management—it’s hard to get management to have “redundant” servers which normally don’t get used.