I'm actually not sure that's true. If the White Sox hold him, and he just manages to not get injured, even if his innings are tapered, he very well may be worth more over the offseason, with a team able to plan around his "full season."
While theoretically getting him now gets you next year plus whatever is in the tank here, the teams that are pushing in at the deadline specifically need something now, so giving up chips for Crochet represents opportunity cost against an alternative. Even if that alternative is inferior, it may be a better fit for the rest of 2024, and you can plan for 2025 when the time comes.