Today 10th Nov 2017 the house iMac was upgraded to OSx 10.11 El Captain having happily run on OSx 10.6 Snow Leopard since in in 2009. Snow Leopard was the last version of Mac OSx that would run PowerPC code ( in emulation mode) so this lays to rest QuarkXPress version 6.5 that was the last vestiges of DTP software used for the other halfs' typesetting business. Purchased as box software many, many years ago Quark has provided good service but is no longer required. Running OS that is over five years old, that no longer get security updates, is also a bit of risk. Also expiring was the last free version of Mac the Ripper DVD content extraction tool. I have to admire Apple by making it so easy and smooth to do an OS upgrade effectively jumps forward five operating system releases in one go.
The smaller handheld Apple devices upgraded to the latest version of IOS 11.0 recently and this has obsoleted early Apps. My favourite APP was ConvertBot, a little gadget that converted numbers between different units. The software was so well designed and looked so slick that for me it became an early demonstrator for Apple's approach to building a software ecosystem. Many other Apps that have not been updated in the last year or few will also have expired and become unusable. More information here.