To explain why there were too few people there. Also if it was a wedding rehearsal, he (QT) could have that brilliant introduction to Bill which is very GBU-like. Also, making it a rehearsal, would open for talks between the Bride and Bill to take place. If it was a proper wedding, there would have been too many people there (as mentioned by Reverand Harmony) and how could Bill possibly talk to the Bride as she would have been too busy.
