To me, the point of learning any grappling style, be it good old fashioned wrestling, BJJ, judo, or the grappling elements in any other art is this: To put the other guy on the ground, where he is at a severe disadvantage, and to stay off the ground yourself.
Good advice, if you are on the ground grappling with one opponent, his buddy will be over kicking you in the head.
The advantage to staying on your feet is to use run-jitsu, because taking on more than one opponent without a weapon, no matter how well trained a person is , is an almost sure lose situation.
that being said, everyone should learn to martial arts skills on the ground and standing up, as Royce Gracie and Jon Bluming have both proven , the most skilled stand up fighter is at a serious disadvantage if he doesn't know any ground work.