in bass fishing what is the point of using one cause if your fishing heavy cover with 65lb Brade with a 20lb mono leader isn't there a better chance of braking off

Yes, but you'll lose only the leader, none of your main line. Also, if you are using braid, a mono or flouro leader is far less visible.

I use the braid for its sensitivity.  I use leaders on it for their invisibility.  I fish clear water and need all the advantages I can get.  I catch a lot more fish with a leader on braid than on just braid.

Yes i use leaders for jigs and if you get a fluorocarbon that was made for leaders the it will be far more abrasion resistant  than a main line flouro

so whats the ideal situation to use a leader

Gin clear water with rocks..