Just as an fyi, since you're using a lack of his experience with karate as an argument... @Hanzou has mentioned extensive (i think over 10 years but might be wrong) training in shotokan before switching to BJJ. So he's got experience training what he's talking about.The benefits of kata (again) are forming a strong stance foundation, footwork and tai sabaki (evasion), teaching good balance and posture, effective form when executing techniques, and last but not least, self-defense against grabs and other attacks.
Kata is not an end to itself, but part of an overall program of various trainings, each lending its own benefits.
Not having done kata or much karate, or understanding the origins and development of same, you do not have a good comprehension of the subject. "Beating the hell out of each other via kumite all the time" leads not to karate, but to brawling.