IBM stuff that survives from the 70s does so because those organizations planned their future hardware and software migrations. z/OS releases are supported for

IBM stuff that survives from the 70s does so because those organizations planned their future hardware and software migrations. z/OS releases are supported for 3 years after release. You then have to update to the N+1 or N+2 version. Windows releases are supported for 11 years. You then have to pay for extended support or update. This has always been the case. This is well known. If you're running an internet connected XP machine and not paying for extended support you have nobody to blame but yourself. It is not Microsoft's responsibility to support all versions of their software indefinitely and for free.