This form of rejection (for surely curving is rejection) is often seen as a way to avoid confrontation or hurt feelings between two parties; one interested in dating, the other not. While it may feel less harsh than an outright "no," it can also create confusion or prolong disappointment for the person being Curved. Open communication and clarity in dating are key, and while curving might seem easier, direct and kind rejection is usually more respectful in the long run.
In any dating scenario, practicing clear communication and respecting others' boundaries helps ensure that no one is left in the dark or feeling strung along.