So, I can't speak to Spanish, but I can speak to French. There, the suffixes that are silent in Metropolitan French are still pronounced in some regional dialec

So, I can't speak to Spanish, but I can speak to French. There, the suffixes that are silent in Metropolitan French are still pronounced in some regional dialects, but the grammar doesn't really change (that I've noticed). That leads me to think that it could just as easily be that grammar changes render the agglutination superfluous, and it subsequently withers away like a vestigial organ.