There are probably several factors, but some of it might be related to how the legal system works.

Even if caught and convicted, you probably won't do much time if you only damage property, and you might not end up in any of the more secure wards.

The time window for prosecution is also different, with only murder/attempted murder having an indefinite limitation time. All other scale with the maximum punishment.

Thus for lesser crimes the state has to prosecute and bring you to court within a certain time, which is shorter the less serious the crime. If the state fails to do so, and the limitation period expires, you can't get charged even if evidence turns up.

Thus many criminals - especially career criminals if my understanding is correct - actually try to avoid - killing, or maiming people is possible. It's not worth the increased risk. At least that was what I was told by someone privy to these matters quite some years ago.

Less likelihood of media or police attention. Maybe the gangs are hoping (or even empirically aware) that authorities will be reluctant to investigate them -- for whatever reason -- if their activities keep under the public radar.