sokker: Since you state that you're a bisexual (cisgender I guess) female person, I admit my great confusion how extremely weird your perception of (cisgender) male bisexuality is. 
Simple facts are: 
Not everyone, who is a cisgender homosexual person, has romantic feelings towards persons of the own gender; some have romantic feelings towards the opposite gender, or towards transgender persons, and, yes!, some have no romantic feelings at all. 
Some bisexual cisgender men are loving husbands of cisgender women, but probably sometimes their sexual drive is focused on one particular guy (who is their «fuck buddy» or «friend with benefits»).
Or e.g.: Some bisexual cisgender men have a strong sexual attraction focused on many women, but perhaps their romantic feelings belong just one particular guy. 
And so on and so on 
 
 
O.K., bankside, can't argue with that & with you, since a) I'm glad to belong to the first group you mentioned and b) you're a JD/JSD, aren't you? ^^