For HTTP, being pedantically correct is a tradeoff. On the plus side, you prevent weird potentially unexpected behaviors by cleanly rejecting off-spec behavior

For HTTP, being pedantically correct is a tradeoff. On the plus side, you prevent weird potentially unexpected behaviors by cleanly rejecting off-spec behavior instead of accepting potentially broken input and seeing what happens. But you also can't interact with everyone else anymore, because a whole lot of people run slightly off-spec software, successfully, and sometimes without knowing it.