I would assume many of those who are interested in the Platinum in the first place, are likely somewhat interested in building up perks and status with hotels. Otherwise, FHR is probably the best use of this return. I couldn't bring myself to book regular hotels under amextravel unless it was one of those areas where there aren't many other options. Like Fort Myers beach for example. You aren't finding many name brands there, negating the whole status build. At that point, amextravel might be a fairly convenient and rewarding option for some.

I just recently booked a trip and immediately went to my usual brands for max returns, perks, etc. Just with my base and bonus earn alone, it was more than a "5% (to 7%)" return. Factor in my credit card, and another cash back portal, and we're somewhere between 15-20%. Same price too. In these scenarios, amextravel would never even cross my mind. Plus, I am probably more likely to get a more ideal room, drink/food vouchers, etc. Some people would likely even value perks and upgrades over cashback (even if it's just the hope of one). Booking direct is still king in most scenarios.