My guess is that they deemed it a little bit too obscure, but I don't know that and can't imagine the process used and there are probably plenty of words in the list to point at and quibble over.

One of the things about Wordle is that it can give you a good shot at a feeling of success. Having something that feels like an "obscure" word which causes you to fail, lessens that positive feeling that could keep players returning every day.