It's reductionist to say all straight men are bi. None of us fit into boxes like that. But it seems even on sites like this where tolerant sexual people congregate that it seems hard for men to say they are bi in some way or another. The stereotype couple here is straight male, bi curious female. Yet on the bi chatrooms you see plenty of 'straight' men either singles or part of couples browsing. I think this is sad. And I think it means men think rightly or wrongly that there are negative consequences to be identified as bi. And women don't seem to face that fear.
For the record, I'm in the group who fall in love with women, admire their beauty, want to kiss, cuddle and cherish them while male beauty does nothing for me. Yet I'm a randy personality and a cock means some sexy time and it makes a great toy and lord knows how you fit labels to that.