Al acabarse la atención se acabó todo no crees?When the attention ended, everything ended, don't you think?

There are many contexts, and therefore, many reasons. I won't even begin to list all the ones I've known about. It's a long list, and not a fun topic. If you communicate regularly with friends and family, you'll be able to take notes.

Men sex, women attention

Both as well as too much time on their hands!

People are unfaithful because true sexual monogamy is incredibly rare in the animal kingdom, even among mammals, "monogamy" is usually just social monogamy (cohabitation for the purposes of raising children). Humans didn't really start doing monogamy until the advent of agriculture. We're trying to...

En mi opinión ninguna de las dos. Es simplemente de escases de principios.