I do agree with you for the most part, progress must go forward, but…
Because as of today 2.81 is in Alpha, but I’d like to acquaint myself with the changes without being marrying to it…yet. Not everyone is a madman (like myself and present company ) and uses Alpha-stage software, so exchanging files becomes difficult (already, only four months after an enormous change).
Because, in my original example, it’s just a Mapping node that’s existed since…gosh, I can’t remember…and really, only the layout has changed (IMHO for the better) but the contained information doesn’t. I don’t understand why a simple UI change results in a “Undefined” node. The Principled Shader node (for example) has changed but there’s no problem there.
Because we as software users have become too used to New Version Incompatabilty Syndrome. Imagine if you had to update your image editing software every time the JPEG/PNG/TIFF/whatever format was updated. Using Photoshop/GIMP as examples, saving in native format .PSD/.XCF you are at least given the option to save in a backward-compatible version or not. An 180° example of this is with Microsoft Word, forcing an (paid) upgrade every time Microsoft updates. You now have incompatible Word 2007 (.docx), Word 2003 (.doc), Word 97 (.doc). Or that other evil empire Adobe, with the Illustrator/After Effects formats. In their defense, at least these major incompatibilities happen once every X years.
So, there are a few reasons why.
Whew! Why are you making me work so hard? PEACE!