Several of you have hit on some of the key reasons I avoid the "aggregator" high annual credit cards (like Capital One, Chase Sapphire, AMEX, others). The coupon and proprietary point systems have inherent flaws to consumers, and built-in advantages to the card companies.
Coupons: Uber, Lyft, DoorDash, etc. are actually profit centers for the cards - they get paid to offer these lead generation coupons, and probably a kicker based on usage. The providers have priced in marketing costs to promote sign-ups and usage of their services, and this is likely a better ROI than advertising or social media for them.
Proprietary "Travel Portals": Also a profit center, to the consumer's detriment. Not only are their fares and rates worse, they are also commissionable and quite profitable for the card companies. They can effectively devalue their points at any time by changing the rates they offer, as well.
Lounge Access: As is readily seen from recent changes, they can adjust access and rules at any time they feel like restricting cardholders from this benefit.
Transfer of Points to airline/hotel chains: As others have stated, this is perhaps the best use of card points, but watch out for restrictions in place or to come in the future. Realize that the card companies get volume discounts on the points/miles, so this is also potentially a profit center for them over their initial pricing (certainly over what it takes for consumers to earn rewards.
Note - I have no grudge against these cards - they're companies trying to turn a profit. But, unless you're careful, you're just paying a high annual fee for "benefits" that are actually mostly a benefit to the card issuer. I prefer to piecemeal out my rewards from the "manufacturer" of the miles/points (i.e. United, Hilton, Hertz, etc.), and cut out the middleman who may change the rules in the middle of the game. Once again, it depends what you're trying to maximize (i.e. lounge access, free trips, discounts), but in most cases, a 2% cash back provides a greater return than these increasingly convoluted aggregation cards.