Grind at clubs?

Why do some guys like to 'front grind' at clubs? I was at a club the other night dancing near this guy and he started to grind with me from behind like most guys do. Then all of a sudden he whipped me around and sort of put one of my legs in between his legs and danced. To me it just felt awkward and stupid. Do you think he was enjoying it? What was he doing exactly.?
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I guess I'm wondering. is front grinding like more enjoyable for the guy than normal or what?
Grind at clubs?
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