Witnesses are not instructed to wear the gear either. They dress up for Zoom, since that is interactive like the meeting. Usually many will watch the convention after the the shortened WT study, so they are already dressed up. If someone wears a badge, then it's for the same reason as was already mentioned by someone, like wearing a t-shirt to support a team. Personally I think wearing a badge is daft, then again I wouldn't wear a team shirt either if just watching it on TV. Some people like to take pictures at the convention for memories sake, so with Covid-19, they will take pictures at home, badge and all, also for memories sake, like hey, do you remember how we all had the convention at home in 2020?
But no one is instructed to dress up to view the convention, which a lot of Witnesses will watch snippets of through the week, some in their pajamas...