There are really two types of Platinum Extras certificates:
1) The kind you get when you renew Plat status every year. These are only good for on property redemption and expire rather quickly, so I can see how many of these go unredeemed. (The ones I've received the past two years, for example, were not redeemed because I had no Hyatt stays prior to the expiration dates.)
2) The kind you get every three stays. Since these can also be redeemed online for GP points, I consider these a good perk and it certainly provides an incentive to make that additional stay at a Hyatt vs. a different chain, since I know there will be some bonus points attached to that threshold stay.
The certs in the first category probably won't be missed too much. However, like the G bonuses, I think the certs in the second category will be missed.