So, to facilitate Macs changing hands, Apple has un-facilitated d/l'ing macOS; their's either something seriously wrong with their logic, or they're "crazy as a fox".
Other posts have stated this, but Recovery Boot Mode provides for ways to install older and current systems, perhaps obviating the need to archive purchases in the App Store:
Only perhaps.
The original setup was all inclusive, while the new one is limited at today's date and will be even more-so as new versions of macOS are released, because with Apple's current release schedule, supported Macs are able to run many more versions of OS X/mac OS than just the three offered in Recovery Mode.
