[toomanythings2]

You are right. The vendor prefixes are there to introduce new properties that they hope will be implemented in the standard. All those prefixes can change or disappear altogether and without notice.

However, this is a way for a browser vendor to test their code in real life. If it fails, they can change the prefix and try again till they get it right. You can't do that once it's standardized. In fact, there are a number of properties that have been implemented incorrectly and still exist today but were eventually fixed in the non-prefixed property.

But a developer is to then remove the prefixed property. Not complain about it and blame others for their decision to use it in the first place.