I always wear boots, always will. The only time I went down on a 2-wheeler, my boots saved me from much more serous damage to my leg and foot. As it was, my lower leg was broken in two places and my foot was twisted around 180 degrees backwards. If I had been wearing tennies instead of tall steel toe boots, I almost certainly would have lost some toes, (the leather on the toe of my boot was ground off, and the steel underneath had deep gouges and scratches) and probably would have had the ends of broken bones digging into the dirt.
Everybody has to choose for themselves how much risk they are willing to take. Bike or trike, I'll wear boots.