Do you report players who break in-game rules or do you not bother? i.e, cheating, trolling, abusive messages, etc? Depends on the severity, most of time it is okay and I don't report them to the company.
I report cheaters and griefers in Counter Strike: Global Offensive via the built in system. It requires a good amount of reports to get that player banned but you never know, maybe he or she will get banned some day. But in another game which I play you need to make a video of the person and report them on the developer's website. I don't have time to do that.