it's just easier to simply add an 'edit mesh' modifier to apply the materials on poly mode, it's not the best approach though. The functionality is already there, a simple checkbox 'assign materials for sub-objects' on the poly editing tools rollout would be very useful or maybe your ideas? It's not a major issue, just a minor annoyance though. Why does not exist in edit poly? but it exists in mesh mode! I dont like using Set ID! I think its that simple to do.
Thanks