I do have Busy Cal..and realise it does work far better than iCal or ML Calendar. It's what iCal used to be!!!!
I created a local "ON MY MAC" Calendar in BusyCal and recreated all my Automated scripts and private events. I can think of 3 great reasons why you would WANT to have a local Calendar that does NOT sync.
Mostly for people who run businesses, have complicated lives and are not "Susie homemakers"...that would be mostly people who are not still living in the 1950s.
Thanks Apple for treating us like children with your uber constrictive downgrades of software!!!