Just read am article on https://www.bloomberg.com/news/articles/2017-03-08/amex-seek… saying that Amex is chasing credit card "games". I don't what percentage if their customers are gamers, but they can reduce this problem with increasing bonuses for existing customers, e.g. by more shop small or statement credit offers.
I am pretty sure that they have a different strategy in the US. Things are very likely to be different for them in Australia.