Premiere 14

14.9 is still available through the CC desktop app.

And so is 13.0

Adobe subscriptions provide current and ONE earlier version

If you need something else, go here

Direct Download Links https://prodesigntools.com/tag/ddl MAY help
-you MUST do what it says in Note: Very Important Instructions
-https://prodesigntools.com/adobe-cc-2015-direct-download-links.html#download-instructions
-the prodesign links go directly to Adobe's file server, so this process will
--only work until Adobe completely removes the old version(s) from the server
.
IF/When you do have a download, be sure to copy it to AT LEAST one external device
-since Adobe does sometimes remove old versions from the server
-a usb flash drive or external hard drive, or write to a DVD

Part of it goes back to some licensing issues with Dolby (I can't remember the version number, I want to say 12 or 13) where they could no longer offer versions containing Dolby codecs they no longer had licensed. I'm guessing at that point someone said "Let's just adopt a no farther back than 'x' previous versions policy" and now here we are.