That's cause it was so unexpected, it was one on the biggest events in marvel cause it was unexpected, just like dark phoenix that was big cause it unexpected.
Actually, that's the theory the Goblin threw at him when he realized Gwen was dead. Peter is more than likely to blame himself for things like this, and it was indeed Spider-Man who hypothesized that he inadvertently killed her in that fashion.
In subsequent situations where civilians and even loved ones were falling from a great height, Spider-Man showed he had learned from his mistake and improved his method so it wasn't deadly to the person falling.
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I'm the best there is at what I do, but what I do isn't very nice.