Mainly because the conservative Catholic part of the CDU was a devoted follower of the 'Kinder, Küche, Kirche' framework - 'a German slogan translated “children, kitchen, church”. In present-day Germany, it has a derogative connotation describing an antiquated female role model. The phrase is vaguely equivalent to the English Barefoot and pregnant.' http://en.wikipedia.org/wiki/Kinder,_K%C3%BCche,_Kirche (not a very good link)

And it is not exactly a coincidence that Merkel is East German - most West German women found more hospitable political homes in other parties, in part because most West German women who wanted to live in ways not encompassed by traditional role models pretty much realized that the CDU was their opponent, at least in the past.

Things change, of course. Now, the Christian Democratic mayor of Hamburg (who while gay, is not in a civil union like the SPD mayor of Hamburg or the head of the FDP) is allied with the Greens to retain power. A generation ago, the CDU was also the most reliably anti-gay party.

As pointed out by Radlafari, the 5 mark tax died, but increased taxation of energy did not.

The Greens are to a major extent being proved correct in their forecasts - I would not say that raising energy taxes is political suicide in Germany, at least as long as it is coupled with positive benefits - the growing number of PV system installations and home insulation standards being concrete examples.

The original Green tax proposal was clumsy, and then whipped into a firestorm by the Bild. What is forgotten is how Kohl raised the gasoline tax several times, without the same accompanying outrage.