I can only speak to my personal experience with Aikido. There are plenty of techniques where punches are used but primarily to tie up or distract your opponents energy (e.g., tsuki kotegaeshi and shomenuchi sankyo ura waza). They are also used as a check for your distance (katadori ikkyo through yonkyo and ushiro ryotedori ikkyo through yonkyo). We also have many variations of pushing underneath the chin with a palm heel that could easily be turned into strikes (and are strikes depending on how you apply them). There are also several variations of koyunage the seem to work the best for me when I have the feeling of punching my opponent in the head as I bring my arm around to face the same direction they are facing before I execute the throw. I miss their face by a good 2" but I could very easily turn this into a punch.
We also learn punches and tegatami (knife-hand) strikes but they seem to be based entirely up on our sword strikes.
As for kicks, I have never seen a kick as a response to an attack. We rarely do work on defense to kicks but are not fomrally trained in kicking (although many of us have other martial arts experience and know how to kick). My sensei explains that kicking, especially above the waste level destroys your balance. It's also very difficult to kick while wearing a hakama
Again, I'm sure there are other people with vastly more experience that I who can provide you with an explanation.