Academics' primary external recompense is in credit, attribution, and recognition. AI has effectively ended attribution, so I'm not at all surprised people are less interested in sharing and publishing. Especially when anything you publish will just be used to train the next iteration that still won't credit you.

Sharing ideas involves communication which happens between two or more brains.

Prompted LLLM output only involves brains on the input side, the source training data. Nothing is communicated to the end user brain because they don’t try to understand the output and never had the knowledge or experience necessary to do so if they wanted to.