Every medication has conflicts and side effects, ranging from vitamin absorption changes to actual risk of death depending on your situation. Adding another medication adds to the complications, in a 1+1=3 kind of way.
The more you keep going, the more you're taking on. Soon it becomes a "do I like living or do I want to kill my liver for X benefit" choice. "Brain-zap effects or suicidal thoughts?" (Or, with effexor, both!)