When the tongue pushes inside, many people feel a deep, full, slightly taboo pleasure that radiates into the pelvis and can connect to prostate (in men) or vaginal/G-spot sensations (in women).
There are Anatomical Benefits of Throat Straightening while deepthroating. When the head is tilted back and hangs off the edge of a bed, the airway and throat change shape in ways that make deep penetration easier