As with all SM, it is feelings that are had when Master takes control and when the slave looses it.
This picture, possibly an extreme image is not unusual when placing yourself with respects to your God like Master.
Many slaves can get off on this image, it depicts the natural state of being for a slave.
This expresses the totally helpless slave, bound good and secure, gagged, so when he inevitable cries out the dirty jocks being roped in place in his worthless mouth makes his pleas for help ineffective.
He has been secured by 'real men', the kind of men that he idolizes. His balls are now in their powerful grip and are really going to get it...
There is something always very special about entrusting your most sensitive parts to you Master. As we know SM is also all about 'Trust Trips', the yielding and the special intimate relationship that exists between Master and slave. There are other examples of where a slaves cock and balls are in a guillotine any any unauthorized movements when the slave is in this bondage will cause the cutters to move - all within the slaves control, he only needs to obey and stay perfectly still until his Master chooses to release him
Cock and Ball Torture address such fantasies in a practical way, like you want to do it often - cutting your balls off is a one way street.
Just as a slave may need to feel the secure grip of his Owners hand around his collared neck, the is also a sense of security to be gained from the Master encircling his hand around the slaves balls sack - "I got you now"