First, boys with abdominal muscles are thinner and more fit, because abdominal muscles need a high body fat rate, which many girls like aesthetically.
Second, boys with abdominal muscles must be very self-disciplined in life, which is also an important highlight of a person.
Third, abdominal muscles are easier to see. For example, it's a bit exaggerated to open your clothes and wipe your sweat when playing basketball.
Above, and attach a beautiful photo of Eddie Peng Yuyan Yuyan.