If you’ve made your own engine or significant unique pieces of technology that’s part of your companies IP which is inherently part of the value of the company.

If you’ve made your own engine or significant unique pieces of technology that’s part of your companies IP which is inherently part of the value of the company. Further to that open sourcing software takes effort and the more complex the software the more effort it takes. Game engines are very complex. Then for most companies they are trying to make and ship games which is also pretty hard. So open sourcing seems like a lot of work for little return. That’s often why engines that become open source are general at their end of life from a commercial perspective. Games with modding in mind often do open source relevant bits to make modding easier.