ORIGINAL: CV2
Actually running away to India or Oz to fight another day fits the bill better than having the troops destroyed [;)]
It fits a different bill.
As the Allies, if you defend Palembang (or other places in 1942), you consider that it is worth having troops destroyed, so long they take a lot of enemies with them, deny early access to needed resources (like oil), and delay or derail japanese expansion plans. The strategic reasoning behind this is that, in the long run, you'll replace lost troops and equipment better and faster than Japan, and that anything lost early in the game takes a while to be replaced anyway, thus reducing Japanese strength during the most important moments of the war (late 42 and early 43). The psychological background is that Japan, in the early game, tends to be proud of its strength, might get dragged into an inefficient slugfest, and will be quite shattered if resistance proves successful.
Evacuation strategies follow a different logic. Just like you say, the idea is not to delay or resist, but run...
This said. Be aware that the first goal of a japanese player in the early game is to guess what strategy the allies will follow. If you know they are evacuating, then your early game goal is to sink as many of the troop transports as you can. You have the resources for that, they can't do it very fast (because AP do not all start in the right places, because they tend to be slow, and because you don't have all the PP to do it at once). If you manage that, you get the best of both worlds : they get destroyed, and they don't fight...
But again, unless you think total evacuation is the only option for the allies (despite many AAR proving the contrary), we are comparing different things here.
Francois