Good point. But in both cases I didn't have time for the horn blasts as I was doing what was expected of me and very close. There is the "Last clear chance" rule so I altered course as I was the captain with the last chance to avoid the collision. Believe it or not in both cases had there been a collision there is a high probability that both captains would have been at fault. The captain that disregarded the rules and the captain that did not avoid the collision.
Yes the rules are setup that generally both parties are at fault. Most recreational boats are at fault by default because they fail to have a separate lookout and person on the helm. Not to labor the point but not doing the five blasts would be chalked up to not having proper lookout for early and effective action.
But what do I know ... I own a french production boat ;-)