Educate me: why all the rusty fenders?

[markeb01]

IMHO the drain hole is big enough, if nothing is allowed in to begin with. Unfortunately GM designed the fenders to collect debris and form a compost pile in the lower fenders until the sheet metals bursts open on the front side. The only way to prevent it in the future is to close all the openings into the fender brace. Here’s how I permanently fixed mine: