I for one don't consider myself a jealous person, but I prefer to know my love's past, and I know she is the one I am truly destined to spend the rest of my life with, and I know that whatever she said, it wouldn't change the way I feel.
I also think it was based on a little male insecurity, because it was my first time when I had sex with my girlfriend, and not hers. It was also partly that she was still married, I wanted to know why she would get married with someone she didn't love. But I guess I just try to understand people too much.
Sorry so lengthy aphrodite24, but I just wanted to put an example of why someone might be happier if you did tell them.