... to encourage many new participants to avoid using a big obvious door (many will follow the nudge of architecture rather than pause to process textual instructions first), to use a process that's new to them (many will default to what they would ordinarily do), to do-ocratically make changes (many aren't used to that freedom), to wear a mask (many aren't used to it), to ask for consent before photographing or forwarding (ditto), etc.
Written signs, posted policies, etc. can *help*. But...