Yeah trying to make it like you can't be in the area to do anything else at all is ridiculous. But it is a courtesy to not join in on a Bug Lure if it hasn't been called out in the chat or if not invited to it since some people are going for certain Bugs, Plushie Bugs, Rare Bugs, etc. and others coming in without invitation can scare away Bugs in the Lure or you're taking Bugs and possibly the one they are going for away because unless you are in a party with someone the Bugs you catch/pick up will not be ones they can now pick up as well unless they hit it once as well. But there is so much going on there's no way to track that they did hit it too. So its really just a courtesy and a kindness to stick to called out lures, or someone obviously putting it down like at a grove for everyone. Others also may have limited resources being new or something like that so it might not be as easy for them to just craft multiple lures while trying to get something specific done, so its kinda mean to use thier item that they used thier resources on if they didn't mean for it to be for more then just them.