Because they WON'T. They don't "have to incorporate surcharges" into their prices anywhere else in the world. And if some try, then competition will sort this out over time. It's rather the opposite, I bet the Hiltons and Marriotts of the world had a line in their global P&L statements saying "Rip off fees for gullible Aussies and Kiwis only" which they now get to lose. That's it.
Again, because it seems to get constantly forgotten in this thread, these fees are non-existing anywhere outside of AU/NZ and prices are not exactly lower here as a result.