Malware analysis, binary patching, research, bounty hunting, developing cheats, etc etc etc. There are a lot of use cases.

I use a similar application to reverse binaries of proprietary software we legally purchase and use. The vendor is sometimes unable or unwilling to document how something actually works or how something could work if it was configured in a certain way.

Industrial espionage.

cracking software - like removing dongles, finding valid registration keys, removing server checks etc