Why don't all the different religous organisations from across the world...?

all have the same big meeting in the same place? Y'know all the "mes" in all different religions? Why not have them all in the same place at the same time? I hear the muslims are pretty faithful to mecca so why doesn't everyone go there once a year seen as they're pretty relaxed about outsiders. Then they could all try each other's culture's alchohol afterwards.