HaLeiVi: If that’s really the idea then why weren’t there bonfires between R’ Shimon and the 17th century? (And if you want to say because the Zohar wasn’t revealed until the 1200s, then you still have several hundred years of no celebrating to figure out).
Avram: For example, firefighters and EMT workers in Israel had to be organized and ready to go at a moment’s notice, which meant preparing a few hours before Shabbos ended. That couldn’t have been done on Friday.