Although, yes, both Dark and Daizi preferred to help Ivy work through her feelings by teaching her names for her emotions, giving her empathy, and by redirecting her. Hopefully, the effort---because it was an effort, it was hard work---would raise her into an emotionally intelligent adult. It wasn't always possible to calm her, and often their tricks and plans would fall on deaf ears, but it wasn't about being able to perfectly handle her tantrums now, it was about building those social-emotional skills. Every interaction was just another building-block. Taking the time to tell her, I know you are mad about this, but this is why it is this way taught her boundaries and helped her understand the world. Letting her cry and just telling her no without giving explanations wouldn't do much to teach her about her rules.
All that said: they were in a relatively busy line, and they had already told her they need to give the toy to the cashier so they could buy it, and that buying it made it actually belong to her. Forcing this poor, minimum-wage employee to participate in their parenting by making them wait until they convinced Ivy to hand over the dolphin while holding up the line full of other tired parents and children would've been obnoxious. Anyway, she'd still learn about how buying things worked purely by experiencing it.
"Right," Dark said, setting Ivy into her stroller after taking her leash off of her, "Are you all ready to go home?"