To the original question, I find sport mode useful when I am passing on the highway, or anytime I just want a bit more "snappiness". Sure, the gas engine kicks in when you hit 3/4 throttle, but in sport mode, it is always there. So I also use it when I want to have fun, feeling more responsive performance or showing off the car to friends. Since I am pretty focused on hardly ever using gas, I don't use it much, but I can see where someone who wants to feel spunkier performance (like a younger me) would use it a lot.
Regarding the behavior of the regen paddles, at first I did not like them, but now that I understand how they work I like them a lot. And I do get a bit annoyed that they stay in a fixed setting in sport mode, which was not my original feeling.
...the more I drive this car, the more I appreciate the engineering trade-offs made by the Honda design team.