Ah, I think I'm with ya now.
WGT only allows us a 3 day window to complete the first round of these multis. All Round 1 action must be completed before Round 2 can begin, so if you forget to register or forget to complete the first round before the 2nd round starts, you'll end up withdrawn from the entire tourney. For the free multiround events, you'll need to make sure you sign up and play round 1 before Wednesday is out.
There's also the fact that there's always a small group of people that sign up for these community tourneys and forget about it. That probably accounts for a few no-shows as well.