I'm empathetic to what you're suggesting — I've published on open science and meta-science specifically, and think open data should be the default norm. The problem with clinical research, though, is that it starts running into conflicting considerations about patient and participant privacy. Even when people aren't patients per se, the focus often involves sensitive information.

You can just say "anonymize it" but that turns out to be more difficult than it seems initially, especially with many questions of interest.

Also, there's often too many opportunities to do science that is of real public benefit that comes with privacy expectations attached for all kinds of reasons. Cases where there is legitimate consented access but an expectation of privacy without data sharing.

People have tried to solve this problem in different ways (for example, methods where someone can analyze data without having access to it directly) and maybe those solutions will lead to a good resolution. But they often have problems of their own (overhead costs associated with providing anonymized remote data analysis), and don't solve all problems (guarantees of absolutely restricted access to personal data).