This is why we have quite rigorous declaration of interest templates for our journal. We need this information to assess whether interests have been managed (by us or the researchers), but we don't view a declared interest as a de facto conflict in any way.
It is interesting (or concerning?) how challenging people find declarations of interest in research. I think our models for them are very weak, and most exposure is via journals that have almost non-existent structures or guidance. 1/2