[wulos]

LTD - you are talking about two completely different crimes here. I would argue that the Bilal Skaf case is much more of an anomaly, rather then simply a part of rite of passage, type affair.
Being a hoon, is far more common accepted(as abhorent as the results of getting it wrong are) then taking part in a gang rape. As such a massive sentence would do little to adjust the mentality, especially amongst young / inexperienced / bulletproof teenagers.
Telling a teenager they will go to 10 years, or 100 years for killing someone will have little effect. The belief being that it simply won't happen to them anyway.