Perhaps the better question to OP is: Given your assertion that there is a market for international premium service on HNL-GUM, which other premium intl. route would you cancel in ordere to supply the aircraft for the route you want?

Put another way, UA (and all carriers) use their aircraft arrayed in a most profitable fashion. UA could pull intl. 777's of the TPAC route and use them between LAX & SFO if it chose, but is that the highest and best use of the aircraft?

The HNL-GUM crowd can complain, but it doesn't appear to cut the pax loads (although we have no idea what the per pax revenues are). On the other hand, the non-O&D traffic such as OP, can choose other routes if they wish.