I think it's a historical thing having to do with the origin of the word. (Haven't verified this though). Because eventhough we now have a standard language the local dialects have different backgrounds the east is Saxon the south is Frankish. (Dutch low saxon, which is not the same as german saxon though has a common ancestor) and there was Frisian.
This is the case for the two genitives. 's is a saxon genitive. In english it's the most common one, in dutch it's possible but sounds less educated than using "van". (Not uneducated though) A case of multiple languages systems surving/making its way into one language.
And I believe you can still see in english remnants of -en plurals.
Im sure I started research on this once, just can't remember what I found unfortunately.
Very interesting are the words appel and aardappel both -s and -en are correct plurals. In case of aardappel both are still commonly used. Appel
Again this is a feeling, haven't checked it yet.
Or a Vrouw like Anouk. The Netherlands top female singer-songwriter. She can sing anything from rock to reggae. She is beautiful even now in her forties. Anouk aside from having a killer range, is also baby moma to six children. While she performs predominantly in English two years ago, Anouk released an all Dutch album, "Wen D'r Maar Aan" or Get Used To It. Anouk is a free spirit, often coming under criticism by the more conservative Dutch people. Wen D'r Maar Aan is Anouk's answer to those critics. It is also a song of empowerment to her followers to be who they are.