They use a polyester resin because it's cheap, easy to work with and hence, more profitable.
Epoxy resin is difficult to work with and more costly, but the overall product is much, much better.
You must see some type of damage because nothing is indestructible. Nothing, including Souris River Canoes, is indestructible. They may scratch when they run over a log or rock. No one has developed a scratch-proof hull to date. But unlike other canoes whose rigid bottoms can gouge, crack or puncture due to an unforgiving foam mat in the bottom or solid, fixed ribs, Souris River Canoes flex right over most obstacles without cracking or tearing the material.