Something about being in the Tropics is hard on shoes. My deck
shoe soles went hard and got so slick I couldn't walk up a grassy slope. The soles on another pair just cracked and crumbled. I've had the soles delaminate and come off on Teva sandals, Keen sandals, Sperry sneaker-style boat shoes, and New Balance walking shoes. On the other hand, my Crocs have held up pretty well.
The problem extends to other polymers, as well. The rubbers on the slingshot I use to chase monkeys out of my banana trees break in two months. The elastic in soccer shorts and bathing suit waistbands disintegrates alarmingly quickly. Some of my wife's friends have resorted in desperation to keeping their underwear in the freezer
to stave of deterioration.
I have no idea why this phenomenon happens--the warm temperatures, something in the air, stronger sunlight? Who knows, but it's a fact of life down here.