As others have mentioned, he hasn't needed to suggest it because that's the official alternative anyway. The next Dragon crew rotation is coming up in Septembe

As others have mentioned, he hasn't needed to suggest it because that's the official alternative anyway. The next Dragon crew rotation is coming up in September, so the current proposed plan is to only send 2 people up, along with the Dragon IVA suits for Butch and Suni, and bring them back when that crew rotates back out in February. SpaceX (afaik) also doesn't have any spare Dragons available for an extra rescue mission right now. One is set to fly their EVA test flight in a week or so and does not have the hardware to dock with the ISS, instead replacing it with an EVA port. A second Dragon is being prepped for a crewed polar flight sometime later this year, and a third one is likely in the process of being refurbished for the crew rotation in February. But also, they can't dock a second Crew Dragon at the station until they undock Starliner, and that is its own can of worms right now (needs a few weeks to update the software for uncrewed operation).