I remember when my wood/fiberglass Old Town OTCA was new, which was a very involved purchase-trade transaction with lots of driving. I took it on Calero Lake in San Jose, CA, with my young daughter. Landing the boat, I scratched it on some hidden rocks. I was so angry that I screamed out a stream of impolite words. I scared my daughter stiff.
That was 14 boats and 14,000 scratches ago. I try to be careful launching and landing, and I wetfoot entries and exits as much as possible. But if you are going to use a canoe, scratches are inevitable, and they will likely be plentiful if you are out in real wilderness, dragging and lining and tracking and rock bashing and smacking trees and dropping the canoe . . . .
I now worry about scratches on the bottoms of my canoes about as much as I worry about wear on the soles of my boots or on the treads of my expensive car tires, or dulling on the blades of my knives and ice skates. Use = friction = wear.
Still, when a canoe is new, and especially when it cost dearly in money or build time, scratchopobia is a normal reflex.