At lest one reason for limits is to get anglers off the river and give others a go.

Back in the 70s, and probably longer, the WDG limit on steelhead and trout (at least) was X. When you caught X, you were done whether you released them or not. You were even required (but many of agents wouldn't cite you for it) to punch a kelt steelhead and count it as one of your two fish. The idea was to get you off the river and give someone else a chance.

The purpose of recreational angling, at least what is SAID, is to offer opportunity to catch a fish. It is not subsistence fishing. There probably does need to be a serious discussion about what a recreational fishery's purpose is. Also, another purpose is to generate economic activity. If one fishery generates $10 per fish caught and another $100 the state will in all likelihood push for the $100 a fish action.