It's a cultural thing I guess. I know some people who think of their maternal lineage as if it were less of a family than the paternal one. Their excuse borders religion and superstitions.

I'm interested though which languages distinguish maternal and paternal grandparents. Just like in English, in Polish you simply qualify[1] if things like these matter.

[1] paternal: po mieczu (sword lineage); maternal: po kądzieli (distaff lineage)