Why does the Bible only refer to angels as male?

There are many mistaken conceptions of angels which are nonetheless popular today.  One of them is how people generally describe angels.

Angels are thought of as having two wings and halos.  They are thought of to be either male or female or both, or as small children (including infants).  The Hollywood film City of Angels depicts them as grown males, all wearing black trench coats.

However, the Bible describes them in a different way.  No haloes are ever associated with angels in Scripture.  They always appeared in the form of grown human males.  With the exception of the cherubim (Ezek. 1:11, 22-23; 10:1) and seraphim (Is. 6:2), angels did not have wings…although they are shown as flying (Rev. 14:6).  (It must also be pointed out that cherubim and seraphim are never specifically classified as angels in the Bible; thus it’s speculation as to whether it would be right to call them angels.)