Still only 2% of men take the leave, while 42% of women do [1].
I can only speculate as to why.
1) Our cultural wiring runs deeper than just "sex is a social construct"
2) The German system is still quite complicated. As countless online calculators and private consultancies helping you filling out the forms prove. As well as the above statistic itself, since financially it would make more sense if the father took as much leave as possible (if he earns more, the family gets 65% of "more").
[1] https://www.destatis.de/DE/Themen/Arbeit/Arbeitsmarkt/Qualit...