It helps to define your terms before philosophizing. I assume that you mean morality(a collection of beliefs as to what constitutes a good life) when you write ethics.

I can't speak for you, but my moral views are originally based on what I was taught by my family and the society in general, explicitly and implicitly, and then developed based on my reasoning and experience. Thus, my personal moral subsystem is compatible with, but not identical to what other people around me have. The differences might be minor (is torrenting copyrighted movies immoral?) or major (is hit-and-run immoral?).

Abiding by my personal morality is sometimes natural (like your "taste"), and at other times requires immense willpower. I have noticed that there is also a certain innate component to it.

Sometimes I change my moral views when new convincing information comes along. I do not think of them in terms of some abstract utility function, but rather as a set of rules of how to be good in my own eyes, though they would probably contribute to one number when properly weighted. I don't bother doing it, though, and I suspect it is the same for other people.

I am yet to see anyone proclaim "My moral utility function spiked from the last week's average of 117 to 125 today, when I helped an old lady cross the street." Sure sounds like something two AIs talking to each other would boast about, though.