Big large pots 20L+ drainage is a must! I use some gravel or small rocks. It helps rinse the silt out the bottom and aids in aeration. That simple.
Small pots you can get away with having great aeration. Though there really is no harm in adding drainage too.
Your biggest compromise is the weight and space it takes up. Instead of nutrient rich media.
An inch or two's worth in the bottom of your pot is nothing.