[raxxorrax]

No, the reason is that people of all genders should feel addressed. There is a female version of programmer (and any other occupation) in German, but you can use the male form to address female programmers too. Some argued that some would not feel addressed correctly.

I have never seen a posting where gender was a requirement. You often saw something like this (rough translation):

"With equal qualifications, female candidates get preferential treatment."

Haven't seen that in a long time and I don't think it was mandatory, but some employers used such a clause.

Don't think I ever saw a gender specific job posting aside from movie roles, dancers, etc.