Why do i jerk off watching videos of older men with big cocks?

I am not sure why i do what i do i would never ever have sex with a man nor am i attracted to men physically by thier looks and would never date a man...BUT i do have a thing for wanting to masterbate with another man 35-50 years of age i would never have sex nor give or recieve oral from a man but i like the thought of being next to another man pref. older just jerking off while watching porn not all mens cocks are good looking by any means but some are a turn on specially big ones obviously so thats deal i have a thing to want to jerk off with another man the site of a hard big oler mans cock jerkign next to me to see is hot like i said i am not gay or bi cause i have no urges or intentions to have sex oral or date a man?