I’ve already answered several questions on this subject, but here’s a quick summary of my view: Epiphenomenalism fails to offer an adequate alternate explanation for the phenomenon it disbelieves –i.e. the subjective experience of making choices and having our bodies respond (at least partially) to our will. In particular, it cannot explain why, given the hypothesis that no part of our bodies is actually under the conscious control of the [fictive?] will, do some parts of the body seem to be under our command, while others, like the heart, do not.
Also, how can one explain the existence of physical skills such as wiggling your ears, playing the piano or juggling? These are highly technical skills that seemingly take willpower to gain. It seems difficult to accept that they are talents our bodies (randomly?) acquire independent of any conscious effort.