Regulations aren't always just about the immediate harm. Some individual violations are harmless or relatively trivial by themselves but absolutely devastating at any sort of scale.
At the same time we are scraping the sea grounds empty, killing off entire species, and about every other country is defending the "rights" of their fishing fleets to continue to do so.
Actually all that trawling at least provides tons of food for people and typically is at least regulated to not do too much harm. Getting a lot of clams from beach for fun does not put food on table.