Czuch:
> Gay couples cannot have 5 children to add to the tax revenues for the
state.... single parent families are
> traditionally not as stable, and
therefore less likely to produce productive tax paying members of
society...
> The state isnt discriminating against gay families
etc, as much as they are simply giving extra reward and incentives
> for
what they think will benefit the state more!

This argument is weak.  In North America and Europe approximately 25% of all couple experience problems conceiving children, and as many as 10% of all couples will not have children in spite of all the reproductive technologies available today.  A combination of environmental and social factors has left many couples childless.  Should their "marriages" be called "civil unions" because they cannot conceive a child and should they lose all rights that married couples have?

As for single parent families, that is an entirely different problem.  Marriages fail, and some individuals never assume responsibility for their children.  My mother was a single mother (my father died when I was 6).  All three of her children went to university.  I am a scientist, my brother is a business executive and my sister is a professional artist.  Are we less productive tax payers?  Some single parent families have serious problems, and other succeed.  This argument was weak also.

The bottom line is:  heterosexuals don't want the concept of "marriage" to be "tarnished" by allowing homosexuals to be able to use the term "marriage" when referring to their committed relationships.  The govenment does not want to allow it for two reasons: to make those I just mentioned happy, and to avoid the extra expense of giving homosexuals the same rights as heterosexuals.  As always, it boils down to money and politics.