Rationale behind ruleset (Updated when asked)
It is your own fault, when a member of your team doesn't show up. It is not fair for the opposite team to suddenly have to deal with a top tier player such as Jayjrod to now carry your whole team. This is an attempt to encourage those who sign up to have substitutes ready to go, or to make it to the tourney. The fact that this is posted so far in advance should help with being able to make it.