The answer to 'why is my drain slow draining' is that a slow draining sink or tub is usually caused by a clogged drain. This can be due to a buildup of hair, soap scum, food particles, or other debris that has accumulated over time. Symptoms of a slow drain include water taking longer than usual to go down and gurgling sounds coming from the drain.
Some common solutions for a slow drain include using a plunger to try to dislodge the clog, using a drain snake or auger to break up the blockage, or using a chemical drain cleaner. However, if the clog is severe or difficult to remove, it's best to call a professional plumber to properly diagnose and fix the issue.