My apologies if this was already explain but...

[Johnist]

'Trials' are different from 'Dungeons'. A 'Trial' is a single battle instance. Trials do not allow you to add members. If people leave (in Ifrit HM) it's usually because of 1 (or more) of these 3 'core' reasons:
A) Party is not fully competent (ie: Players have FATE Ground to 50 and haven't learned their jobs or rotations).
B) Party is Undergeared (Titan HM Requires 3200+ Health minimum during Phase 5).
C) Party is not learning from their mistakes.

[Reiterpallasch]

'Trials' are different from 'Dungeons'. A 'Trial' is a single battle instance. Trials do not allow you to add members. If people leave (in Ifrit HM) it's usually because of 1 (or more) of these 3 'core' reasons:
A) Party is not fully competent (ie: Players have FATE Ground to 50 and haven't learned their jobs or rotations).
B) Party is Undergeared (Titan HM Requires 3200+ Health minimum during Phase 5).
C) Party is not learning from their mistakes.

D) A 15 minute penalty is nothing to someone who just wants to destroy the time of 7 other people.

Tanks and healers will get a new group quickly, but those 4 dps will likely have to requeue and possibly sit there for an hour + all because someone wanted to be "that guy".

Because they don't want ppl to join a Primal battle when the Primal has 5% HP left.

They could always just make it so people can only join while the group is out of combat.