It's not always easy to combine the different requirements for those companies.

Some companies have trackers/advertising in their software. In that case, puting them open source would mean that everyone would see the code and be unhappy about the adverts.

Another issue is pirating. Open sourcing the code could maybe allow easier pirating, either by removing the trackers/adverts or by just not buying the software.

Managers can also not know, or not care about open source.

Another issue is that open sourcing it in a way where someone can modify it, may create issues with some people trying to redistribute the software, even if the licence doesn't allow that, which would create more legal work for those companies.