That's cute... no more excuses.. Good stuff.
How's this as an excuse? Work, Family?
The ability for some people to schedule off "blocks" of time each week is impossible (on the same day and time each week for years). Even if it's just 2 hours twice a week. Some people's schedules aren't that flexible.
Thus, the idea of a raid finder allows people to form a quick group whenever they have time. And, it allows them to also leave a group quickly without consequence. Try leaving a organized group quickly? You'll never get invited back or you'll let people down.