Why do we not make a Bracha (e.g. every morning) on the mitzvah of honoring one's parents?
I think with most mitzvos between man and fellow man (bein adam lachaveiro) there's no bracha; I believe it has to do with "how do we know you're doing it for the sake of the mitzva?"
But with regards to the question of why no bracha over saying the Passover Hagadah, they point out that to say "okay G-d you commanded me to show gratitude so now I'm doing it" doesn't sound right. So imagine it:
"Chaim, can you please bring the groceries?"
"Um, wait a minute Mom. Thank you Hashem, you COMMANDED me to honor my parents ... Okay Mom yes I'll bring in the groceries."
The thought process should be a bit more natural!
Also, it's further complicated (as it is with many acts to fellow man) by the fact that a given action may or may not be kibud av v'em. You can feed your father the finest aged steak and degrade him ("just eat the food and be quiet, old man!"); or you could have him hard at work at the millstone and still be honoring him ("if not for the millwork they would have drafted you, I'm so sorry dad.")
We do not make a Bracha on Kibud Av Vaim as by each person the Kibud manifests itself differently.