Why Bisexual Not Known Much

As to bisexual,many people might not know or even not have heard it.Actually,bi exists a long time,but there must be some reasons make it not known to public.In my opinion,not many bis come out is the important reason.But why they wouldn't come out?

everyone like beautiful things

Reason 1:some people may not realize .When they like the person with same sex,they may think it just because they have good friendship.
Reason 2:When someone find him/her like both men and women,they are scared,due to the lack of universal knowledge,they would think it too embarrassed to tell others.So if they hide their emotion deep,no one knows their bisexual features.
Reason 3:In the society,most people are heterosexuals,once someone realize him/her a bisexual,they may feel like them monster because they are different from others.So they won't admit their bisexual identify even hate it to be a bi. 
Reason 4:When people admit his/her a bisexual,many people think it weird ,they can not understand it even feel antipathy to it.They would keep bis away,ignore what their feeling and even discredit them everywhere,which hurt them deep.
Reason 5:Most bis are burn with it,they have no choice to be bi.But if there are not many people support them,they don't dare to come out.They may receive much education about heterosexual instead of bisexual in their growth,so it's hard for them to find someone to know more about it and understand it.
As time going on,gay and lesbian are accepted by plenty of people,why can't them accept bisexual?Everyone has the right to choose the right person to live with,please give more care to them.