I agree!
The limitations with civil unions becomes legal and financial entitlements (e.g., social security benefits, filing taxes; medical and inheritance rights). There are many senior citizens who now "live together" because of financial reasons.
On the other hand, the high rate of divorce and couples living together unmarried have actually been the most significant factor in the alteration of traditional marriage. Maybe all this hoopala about gay marriages keeps us from missing the real changes in our society.
The problem with redefining marriage, is that once you allow for this or that group, then you open Pandora's Box for every weirdo group (e.g. multiple partners, marry your sheep, or dog or whatever!). Don't change the definition.
You want 'benefits' of getting married? Get married!
You want freedom from rules of marriage? Stay unmarried!
Want Inheritance? Get Married.
Don't like it? Stay single.
Know the rules and work them for what you want, just don't whine because society won't change for you.