This could all be avoided if people in a shul welcomed guests and helped them find a seat, siddur or anything else they might need.
This could be avoided if a shul with 40 seats and 38 regular mispallelim was expecting an additional 25 mispallelim for a simcha, planned accordingly by bringing in extra chairs and/or siddurim. If there is no physical space to do so, that is poor planning on the part of the baal simcha.