Hindsight is always 20-20. We weren't there and I think it accomplishes little to try and second guess why someone makes a certain decision unless you are trying to learn something from it. Shackleton was stuck in one of the most remote, inhospitable places in the world, with absolutely no hope of any outside help, and in a situation that almost defied description. The fact that anyone at all came back from that 1915 expedition is amazing and the testament to a leader of the highest caliber, who focused on getting his men home against impossible odds.