this rarely happens to us, especially when everyone that does caravan actually want to participate for various reasons. SB gears, leech experience ( if your actually too far from the fight, you dont earn experience ). my server, though im not doing a very good job ( i am admitting it ), GC exclusive linkshell ( probably not the first to ever thought of it ). i actually encourage xp leechers ( level 40 + ) because they earn seals and exp and atleast have a party. also encourage spirit bonding, only take 4 run to fully SB a fresh gear.

now, if you have those none social players, despite the persistance of you trying to invite them to your party, well that cannot be help, one way is to actually not do the carvans and "take a break" and let see if the player actually does the caravan or drops it. but i agree, there has to be a way to not give rewards to those who does caravan and then refuses to do the run and not even join the caravan party that was forming ( ive seen it before in 1.20 ).