I received a notice from Active Trans that the 2016 Boulevard Lakefront Tour has been cancelled. Why?
Can't speak for ATA, but I suspect: dwindling interest, inconsistent branding (BLT, 4 star, 4 star bike and chow, BLT), difficulty charging people to ride on roads which they are free to ride themselves, and a poor ROI.
Personally, I have always enjoyed this ride, regardless of the name, as it gave me an excuse to explore parts of the city I would not otherwise see.
Lots of rides can afford you that opportunity. Perimeter Ride. Lee Diamond's neighborhood bike tours, Chicago Architecture Foundation rides...