I don't mean to be a dick, but your statement screams you're a virgin. Of course you don't get the same stimulation as on the glands, but it still feels amazing and is great for foreplay. Sex isn't a race.
It's super hot because it's super intimate - the girl's sticking her head between your legs to suckle on your pouch; it makes plain how hot she is for you, how comfortable she is with your body, and how she will debase herself to you to lavish you with affection and give you pleasure - it's a delight mentally, physically, and emotionally.
Some people have different levels of sensitivity. For many, it feels very good.
It shows how much she likes you and is willing to pleasure you. Sucking on your balls; something that most are willing to neglect. It also feels nice when she wraps her lips around my balls.
Mahotama is pretty good for this stuff.
I'll join this convo by saying it's sorta like the Handjob is the actually satisfying act while the ball cradle/play is the extra sexiness (and comforting) that sends you over the edge. Like when my girlfriend gives me a handjob, it feels great. But when she plays with my balls it just adds an extra playfullness to it. Like she WANTS to be doing it for me.
The artist is sethxzoe, and the character is Farah, from Legend of Queen Opala.
That's from Tokyo Lover.
Source is Mahotama.
Hawt. Got one where she's licking a volleyball?