I just don't get how we still allow closed source operating systems for critical business tasks. Maybe I'm a bit behind the times, but some collection of VM, M

I just don't get how we still allow closed source operating systems for critical business tasks. Maybe I'm a bit behind the times, but some collection of VM, MVS, OS/390 aka zOS, CICS, IMS, DB2, RACF, SNA, Oracle, SAP etc etc is probably running the majority of America's critical business tasks. Did it all get open sourced when I wasn't looking? Needless to say, Google Docs and Gmail are not open source either....