Biker "wars" have been ongoing since the late 40s, early 50s and still happens today. Reason - they are gangs and fight to protect their "turf." They are just "taking care of business." Having said this, I wish to add that there are no gangs in Singapore. My definition of "gang" is a group where members take part in criminal activities to make money for the organization. This would be narcotic manufacture and distribution, gun running, money laundering, prostitution, kidnapping, extortion, gambling and similar illegal stuff. Well, actually there are such activities in Singapore but the scale is miniscule, whereas in North America, the market (eg. for drugs) runs into millions if not billions of dollars. And upon seeing rival gangs in their territory, they will kill. Just a few years ago, a massive fight took place between the Hell's Angels and the Mongols at a casino in Las Vegas, shooting and wielding knives openly. In Montreal, Canada, a war between the Hell's Angels and the Rock Machine lasted for months, when the police finally stepped in to stop it after a bomb planted by one of the gangs killed an innocent boy who was at the wrong place at the wrong time. In Toronto. it is illegal for motorcycle gangs to display their "patch" (logo) on their jacket and wear it into a public bar, this is to protect the public.
The funny thing is that, these biker gangs have impacted the public and made the working class guy want to look "cool" by donning outlaw motorcycle gear. Just look at member of HOG (Harley Owners Group). These white-collared yuppies follow the dress-code of the Hell's Angels on weekends, wearing bandanas, sleeveless leather jackets, and try to look like outlaw bikers. Well, more power to them if it make them feel good, but they are definitely not One-Percenters!
Cheers!