Simple: It’s because good guys go to heaven. But the bad boys go everywhere!
Other than that: Good guys use their tongue for talking to tease the good girls. Bad boys use their tongue someplace else to tease the good girls.
On dating: Good guys take the good girls where they are presented as trophies. Bad boys take the good girls where the sun don’t shine.
These few messages have been presented by a bad boy (well, graduate na).